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diff --git a/79263-0.txt b/79263-0.txt new file mode 100644 index 0000000..3692395 --- /dev/null +++ b/79263-0.txt @@ -0,0 +1,1600 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 79263 *** + + + + + LITTLE BLUE BOOK NO. 860 + Edited by E. Haldeman-Julius + + Our Insect Enemies + + Vance Randolph + + Drawings by Peter Quinn + + HALDEMAN-JULIUS COMPANY + GIRARD, KANSAS + + + Copyrighted, 1925, + Haldeman-Julius Company + + + + +CONTENTS + + + Page + + Houseflies and Their Kindred 4 + + Mosquitoes and Disease 28 + + Life Among the Bedbugs 43 + + Lice, Crabs and Cooties 47 + + Our Friend the Cockroach 54 + + Chiggers, Ticks and Fleas 57 + + +PRINTED IN THE UNITED STATES OF AMERICA + + + + +LIST OF ILLUSTRATIONS + + Page + + Fig. I. The Metamorphosis of the Housefly (_Musca domestica_). 12 + + Fig. II. Malaria and its Carrier. 33 + + Fig. III. Three kinds of Lice. 51 + + Fig. IV. Some Common Cockroaches. 58 + + Fig. V. Chiggers and Ticks. 61 + + + + + + +OUR INSECT ENEMIES + + + + +HOUSEFLIES AND THEIR KINDRED + + +The common housefly (_Musca domestica_) is perhaps more thoroughly +domesticated than any other insect; it lives and flourishes wherever +man has established his settlements, and does not thrive elsewhere. It +is mentioned by many of the ancient writers, and has evidently been +associated with man from the remotest antiquity, doubtless adapting +itself gradually to his changing modes of life. It still breeds in the +refuse which accumulates about his buildings, and still invades his +home to partake of his food. When one considers the number of flies +which get into modern dwellings despite glass and wire and modern +insecticides, it is difficult to understand how our sturdy fathers +managed to survive the summers in mediaeval Europe. Picture Thomas +Aquinas battling with swarms of flies for his food! The housefly’s +favorite breeding place has always been in horse manure, and man has +until recent years had great quantities of this nutritious substance +about him; with the coming of the automobile this condition has been +changed somewhat, but even the cleanest of American cities still +affords sufficient decaying matter to assure a bountiful crop of flies. +At some future day perhaps we shall have cities so spotless that there +will be nowhere a speck of garbage large enough to nourish a maggot, +but that day is still to come, and it doth not yet appear what we shall +be. + +Meanwhile, as Herrick says, the housefly is with us always. “They are +present from early spring to late fall, even remaining far into the +winter. They are troublesome in kitchens and dining rooms because of +their abundance, their proneness to get into food, and their generally +filthy habits. Until recent years the housefly has been generally +regarded as somewhat of a scavenger and has been considered of value +to humanity because of its aid in the removal of wastes that are a +menace to human welfare. The eggs of the housefly are often deposited +on decaying vegetable matter that is allowed to accumulate in the +vicinity of human habitations and the maggots that hatch from the eggs +live on this decaying matter and aid in destroying it. Thus it must be +conceded, perhaps, that houseflies do assist somewhat in the removal of +foul and dangerous waste matters and, to this extent, are of benefit. +On the other hand, it has been conclusively shown that this modicum +of benefit is greatly overbalanced by their role in disseminating +dangerous diseases. It has been shown that houseflies carry the germs +of cholera, typhoid fever, cholera infantum, and tropical dysentery on +their feet, legs, bodies and in their digestive tracts. There can be no +doubt of the responsibility of the housefly for much sickness and many +deaths.” + +Although the adult housefly is equally fond of fresh and putrid matter, +flitting from filth to food and back again, the eggs are always laid in +decaying substances, preferably horse manure. In the absence of this +delicacy the eggs may be deposited in human excrement, or even cow +manure if it is not too dry. A single female fly often deposits one +hundred and fifty eggs at a single sitting, and lays as many as six or +seven hundred in the course of a season. + +The egg is white and shaped like a grain of wheat; it measures +about one-twentieth of an inch in length, and hatches in from ten +to twenty-four hours, the period of incubation varying with the +temperature. The second or larval stage is represented by a wormlike +creature called a maggot, which crawls about and devours great +quantities of nourishing manure. When the maggot is about five or six +days old it has attained a length of nearly three-eighths of an inch, +and transforms into the pupa; it is no longer active, ceases to take +food, and the outer skin turns into a hard, brown, dry case called a +puparium. After five or six days of rest the puparium is burst open and +the adult fly crawls out. + +The newly emerged flies mate within two or three days, and the young +females are soon laying their first batch of eggs. Thus the whole +development may occur in about fourteen days, and Herrick thinks that +in Washington, D. C., it may be complete in ten days or less, according +to the temperature, with ten or twelve generations in a summer. “One +can hardly realize,” says Herrick, “the enormous numbers that such +rapid development is capable of producing. Inside of two months, one +female fly can give rise to many millions of progeny. For the purpose +of illustration, we will assume that a female fly lays 100 eggs. If +these hatch and all the larvae come to maturity, about one-half will +probably be males and the other half females. Then at the end of the +first generation there will be fifty egg-laying females. At this rate, +at the end of the eighth generation there would be produced about +1,875,000,000,000 adults. Of course, in nature, a very large part of +these would die before reaching maturity, so that actually one female +would probably never produce such an enormous number of individuals. +However, even under normal conditions tremendous numbers are produced.” + +The adult housefly is unhappily too familiar to require a lengthy +description. The total length is about one-fourth of an inch, there are +two membranous wings and six hairy legs, while the thorax is gray with +four dark longitudinal stripes above. Besides the hairs and bristles on +the body and legs, which entangle great numbers of germs, the sticky +_pulvilli_ of the feet gather bacteria as if they had been especially +developed for that purpose. Thus every housefly scatters bacteria +broadcast wherever he goes; one has only to allow a fly to walk +across a plate of sterile gelatin to see large colonies of bacteria +produced in every foot-print. Esten and Mason’s examination of some 400 +specimens showed that the number of bacteria carried ranged from 550 to +6,600,000 per fly, with an average of nearly a million and a quarter. + +The general impression is that the housefly does not travel any great +distance from its birth-place, but there is considerable doubt +about this matter. Hewitt has taken them flying at least eighty feet +above the ground, and it is obvious that small insects which rise +so high may be carried long distances by the wind. Copeman, Howlett +and Merriman have attacked the problem by marking large numbers of +specimens, releasing them, and then watching for them in traps set at +various distances; they recovered several which had travelled more than +three-fourths of a mile. Dr. Hodge found plenty of houseflies on the +cribs of the Cleveland waterworks, which are located six miles out in +Lake Erie, and which offer no breeding places for flies. He naturally +concluded that they were blown six miles by the wind. + +It has been pretty well established that adult flies do not retain +and disseminate disease germs which they swallowed as maggots in the +manure, but only those which they acquire in the adult state. It has +been definitely proved, however, that the bacilli of typhoid fever are +carried on the bodies and legs of houseflies, and also that the bacilli +are often swallowed and survive the passage through the body, as living +bacilli have frequently been demonstrated in flyspecks. The most +important practical consideration is, of course, the actual frequency +with which houseflies do transfer pathogenic organisms from filth to +food intended for human consumption, thus spreading disease, and this +is in its very nature a difficult matter to investigate. + +Typhoid fever is a disease affecting the intestines, and the bacilli +which cause it frequently remain in the body for long periods after +the patient has apparently recovered. The germs are passed out in the +urine and fecal matter. As Herrick puts it: “If the excreta or urine +containing these bacilli are deposited where they are accessible to +flies, for instance in open privies, the chances are high that the +bacilli will be carried on the bodies of these insects back to the +kitchens and dining rooms and be deposited on our food. During the +Spanish-American War, flies were traced by their whitened feet from +the lime-sprinkled, open latrines or privies to the dining tables of +the soldiers in camp. It makes one shudder to think of the thousands +of open closets in the small towns of the United States to which flies +have access and in which they breed and from which they may come direct +to our kitchens and dining rooms.” + +Excluding the greater variability of the water supply, the fact that +typhoid is so much more prevalent in country districts than in the +city may be due almost entirely to the abundance of flies, since +other opportunities for infection are no greater than in the city. +Certain South American cities have very good water, but typhoid rages +nevertheless, because the natives expose their excreta within a few +feet of the street markets, and myriads of flies carry the bacilli +from the dunghill to the food. “In our own country,” says Brues, “the +seasonal incidence of typhoid fever corresponds to some extent with fly +prevalence, and still more significant is its greater summer prevalence +in regions where systems for sewage disposal are not generally +installed.... The greater uniformity throughout the year in New York, +where the opportunities for fly-borne infection are curtailed, is very +marked. Another way in which the housefly can aid in the spread of +typhoid is through infecting milk on dairy farms where carriers are +present and offer the flies a chance to become infected.” + +The vessels in an ordinary country dairy are nearly always more or less +accessible to flies, and warm milk is an excellent medium in which to +cultivate bacteria. When a fly which has been feeding on the excreta +of a typhoid patient falls into a can of milk, there is a very good +chance that the disease may be spread all along the milkman’s route. +Dr. Taylor, of the Colorado State Board of Health, reports a case of +this sort: “In the city of Denver we had a very sad as well as a plain +demonstration of the transmission of typhoid fever by flies and milk. +Early in August of this year the wife of a dairyman was taken with +typhoid fever, remaining at home about three weeks before her removal +to the hospital, August 28. During the first two weeks of September we +received reports of numerous cases of typhoid fever in the northern +portion of Denver, and upon investigation found that all these cases +had been securing their milk from this dairy. + +“An inspection of the dairy was then made, and in addition to learning +of the illness of the dairyman’s wife, we also found the dairyman +himself suffering with a mild case of typhoid, but still up and +delivering milk. The water supply of the dairy was fairly good. +However, we found that the stools of both the wife and husband +had been deposited in an open privy vault located only thirty-five +feet from the milk house, which was unscreened and open to flies. +The gelatin cultures exposed for thirty minutes in the rear of the +privy vault and in the milk house among the milk cans gave numerous +colonies of typhoid bacilli, as well as colon bacilli and the ordinary +germ-life. The source of infection in the dairyman’s wife’s case is +unknown, but I am positive that in all the cases which occurred on this +milk route the infection was due to bacilli carried from this vault by +flies and deposited upon the milk cans, separator and utensils in the +milk house, thereby contaminating the milk. The dairyman supplied milk +to 143 customers. Fifty-five cases of typhoid fever occurred and three +deaths resulted therefrom.” + +As long ago as 1873 Dr. Nichols noted that the number of cholera cases +on his ship seemed to vary directly with the abundance of flies. Later +experiments demonstrated the presence of the cholera bacillus upon the +bodies and in the excreta of flies fed upon cholera-infected material, +and it has been shown that flies sometimes transfer the cholera bacilli +from human excreta to milk. Dr. Tsuzuki, of the Japanese Army Medical +Service, found the germs of cholera upon flies taken in cholera-ridden +houses, and demonstrated that flies carry the organisms from place +to place. Macrae, commenting on an outbreak of cholera in a jail in +India, remarked that the place was infested with “a plague of flies ... +which were present in swarms when the disease broke out, and it was +an observation of daily experience to see them settling on cholera +stools whenever possible.” Dr. Macrae goes on to say that the flies +undoubtedly carried the cholera germs to the prisoners’ food, and adds: +“The practical lesson is, that flies should be looked upon in the light +of poisonous agencies of the worst kind during cholera epidemics, and +it is clear that if they find access to poison they will carry and +distribute it, and every possible means should be taken to prevent +their getting into contact with either food or drink of any kind, and +to those having to deal with large bodies of men it is a lesson more +easily learnt than put into practice.” + +Because of the flies’ liking for expectorated saliva, it has long been +suspected that tuberculosis may be carried about by these insects. +Several investigators have carried out experiments in which flies have +been fed upon the sputa of consumptives, and the tuberculosis bacilli +have been found in their intestines and fly specks. Frederick T. Lord, +after a long series of laboratory investigations, concluded that: “(1) +Flies may ingest tubercular sputum and excrete tubercle bacilli, the +virulence of which may last for at least fifteen days. (2) The danger +of human infection from tubercular fly specks is by the ingestion +of the specks on food. Spontaneous liberation of tubercle bacilli +from fly specks is unlikely. If mechanically disturbed, infection +of the surrounding air may occur.” Dr. Lord goes on to suggest that +“tubercular material (sputum, pus from discharging sinuses, fecal +matter from patients with intestinal tuberculosis, etc.) should be +carefully protected from flies, lest they act as disseminators of +the tubercle bacilli. During the fly season greater attention should +be paid to the screening of rooms and hospital wards containing +patients with tuberculosis and laboratories where tubercular material +is examined. As these precautions would not eliminate fly infection by +patients at large, foodstuffs should be protected from flies which may +already have ingested tubercular material.” + +[Illustration: + + Fig. I. The Metamorphosis of the Housefly (_Musca domestica_). A, + eggs, considerably enlarged; B, young maggot; C, puparium; D, pupa; + E, adult. +] + +Numerous British army surgeons long ago hazarded the guess that flies +carry dysentery, but the first clear case is that of an epidemic which +occurred in the Worcester State Hospital in 1910. Houseflies were +especially abundant at the time, and Dr. Orton, after a painstaking +experimental study of the affair, concluded that flies were entirely +responsible for the epidemic. + +There is now a fairly general agreement that flies spread the organisms +which cause the infantile diarrhea known as summer complaint, which +kills more infants than any other single cause except lack of +sufficient and proper food. Fraser, Nash and others have noted that the +more flies the more cases of summer complaint, and Sandilands explains +the immunity of the children of the rich by the smaller number of flies +in their houses. It is certainly true that the mortality of bottle-fed +infants is very much higher than of breast-fed babies, but whether +Jackson is justified in attributing this mainly to the infection of +cow’s milk by flies is a question. + +Lucian Howe has long contended that purulent ophthalmia--the sore-eye so +common up and down the valley of the Nile--is distributed mainly by +the housefly. The disease is always most prevalent where the flies are +most abundant, and in flyless desert regions there is practically no +ophthalmia. The natives are singularly dirty and indolent, and flies are +often seen to settle undisturbed about a pair of badly infected eyes. +Dr. Howe has captured a number of these flies, and found that their +feet were covered with the same bacilli found in the secretion of the +inflamed conjunctiva. + +Braun, Demetriades and others report that gonorrheal and other eye +infections are often carried by houseflies. Welander, in 1896, +according to Howard, “observed an interesting case where an old +bed-ridden woman in a hospital became infected. It seems that her bed +was along side that of another patient who had blennorrhea, but that +a screen which did not reach the ceiling separated the beds. Thus all +means of infection except through the agency of flies was apparently +absent. The investigator found that flies bore living gonococci upon +their feet three hours after they had been soiled with secretion, since +they infected sterilized plates with which they came in contact.” + +Nuttall and Jepson, after reviewing the entire literature of the +subject, think that “the evidence regarding the spread of Egyptian +ophthalmia by flies appears to be conclusive, and the possibility of +gonorrheal secretions being conveyed by flies cannot be denied.” + +Bubonic plague is now definitely known to be spread by fleas which are +parasitic on rats, but many observers still cling to the view that the +housefly also acts as a distributor. It is certainly true that flies +are killed by feeding upon the bodies of persons who die of the plague, +and Yersin, at Hong Kong in 1894, showed that these dead flies contain +active plague bacilli. Whether the fly plays any serious part in the +actual spread of bubonic plague is still a mooted question. + +The housefly has plenty of natural enemies, but they do not seem to +reduce the number to any material extent. One of the most destructive +is a minute fungus which grows inside the fly’s body until it finally +causes death. The dead flies one finds on window panes in the fall, +surrounded by a whitish ring, are the victims of these fungus growths. +There are several species of these fungi; in some cases at least the +attack begins with a spore which attaches itself to the outside of the +body, and grows a long thread-like root which enters the body through +one of the spiracles or breathing pores. + +Several species of protozoan parasites have been found in the +intestines of flies, along with a few minute parasitic worms, but +they are not known to cause any great amount of inconvenience. Small +red mites are often seen fastened to flies’ bodies; some of them are +true parasites which suck the juices from the body of their host, and +look very much like the chiggers which annoy the higher animals in the +Southern States. With other mites, according to Howard, “the flies +simply act as aeroplanes to carry the mites from one place to another. +A free ride seems to be the only object for which they have attached +themselves to the fly.” + +Spiders, if given an opportunity, destroy a great many flies, but as +the webs are usually destroyed by the housekeeper’s broom they do very +little execution. The little centipede known as the water bug kills a +great many flies, but as it works at night gets little credit for its +good offices. + +Hornets are sometimes seen to capture and carry off houseflies, but +it is doubtful if any great number of the pests are killed by these +insects. An English entomologist named Westwood once circulated a story +to the effect that “the Americans, aware of their service in destroying +flies, sometimes suspend a hornet’s nest in their parlors.” A little +later one Benjamin D. Walsh, an American, wrote that “some persons in +America have turned the insect-devouring propensity of the hornets to +good purpose by suspending one of their nests in a house much infested +by the common housefly. In such a situation we have been told that they +soon make a clearance of the obnoxious flies; and so long as you do +not meddle with them they will not meddle with you.” To me these two +quotations are the sheerest nonsense; any one who has any acquaintance +with hornets will find it difficult to visualize an American farmer +intentionally filling his house with hornets for any reason whatsoever. +I have never been able to find anybody who has tried out this method; +if there are any such among my readers I should like very much to hear +from them. Please address me in care of the publisher of this booklet. + +The logical way to combat the housefly would be to destroy the eggs and +maggots as we do in the case of the mosquito, but it is not practical +at present. In rural districts, where the dung of livestock is always +lying about, and the human excreta exposed in shallow open closets, +very little progress has been made. Of course, the danger of typhoid +may be avoided by keeping the excreta of typhoid patients where flies +cannot get at it, and the flies certainly could not spread tuberculosis +if no tubercular sputum was exposed. These facts are taken advantage +of in the cities, where there are plenty of flies, but very little +typhoid, because the water closet system is such that flies cannot get +access to the excreta. In communities where there is no adequate sewage +disposal and where flies are plentiful, the individual can only screen +them out of his own dwelling as best he can. Howard estimates that more +than $10,000,000 are spent every year for screen wire in the United +States alone. + +Many ingenious devices for destroying flies inside houses are on the +market--poisons, sticky fly paper, fly traps and fly swatters. One +of the most useful of these is sticky fly paper cut in strips and +suspended from the ceiling. This will often clear a room of flies +when the ordinary sheets of the same paper lying flat on a table are +quite inefficacious. In Japanese hospitals, says Howard, “they take +a whole potato and stick it full of toothpicks, put fly paste on the +toothpicks, and hang the potatoes from the ceiling over the patient’s +bed on a cord. The flies all gather on the potato, and when it is full +they throw the potato away and make a new trap. The toothpicks are +placed about one-fourth of an inch apart, and the potato presents the +appearance of a porcupine.” + +C. F. Hodge is all for building large traps and placing them out of +doors in early Spring, arguing that a great many newly emerged flies +are thus caught before they reproduce, and that it is better to catch +one fly in the Spring than thousands in the Autumn. Brues even says +that “practical traps whereby fly-larvae in stored manure may be caught +and destroyed before transformation have also been devised.” + +Some progress has been made in the treatment of manure piles with +poisons. Howard found that either chloride of lime or kerosene kill +the maggots all right, but the cost of both is prohibitive. Davis +worked with iron sulphate and reported that manure could be cleaned +of maggots and deodorized at a cost of about two cents per horse per +day. Howard, Herns and others have advocated fly-tight pits or bins for +the reception of manure, and these have been adopted in many places, +particularly in California. The regulations of the District of Columbia +specify that all manure must be kept in “covered receptacles,” and it +has been found that a tight-covered barrel suffices for a one-horse +stable. Some workers in the Federal Department of Agriculture have +carried out a series of experiments indicating that borax, hellebore, +and calcium cyanide are highly destructive to maggots in horse manure, +and it is quite probable that some very cheap and simple treatment will +soon be developed. + +The proper disposal of human excreta is another problem that is vitally +connected with the checking of germ-laden flies. As Howard says, “the +average person in the large city has no idea of the fact that there +are many comparatively intelligent citizens who in sanitary matters +have not even reached the grade of civilization which demands the +sanitary privy. Stiles, in the course of his great work in the Southern +States, has brought together some startling figures. He is responsible +for the statement that of 4,825 farm houses in six different states +2,664, or fifty-five per cent, have no privies of any kind; of 2,499 +houses inhabited by white people, thirty-five and three-tenths per cent +have absolutely none, and of 2,326 inhabited by negroes seventy-six +and eight-tenths per cent have none. And what shall be said of the +condition of a large part--the very great majority--of those which +do exist? The uncared-for privy is still a most important factor all +over the United States, even in portions of our most cleanly cities.” +Herrick points out that “there is no longer any excuse for the old +open box privy, cleaned out once a year. It is a menace to every house +in the vicinity as well as to individuals living perhaps hundreds of +miles away because of its possibilities in contaminating milk. Some +form of sanitary closet must be substituted.” One of the very best is +that designed by Stiles, and described in Farmer’s Bulletin 463, U. S. +Department of Agriculture. The bulletin is free, and the privy can be +built at a cost of five or six dollars. + +Another fly which looks almost exactly like the ordinary housefly +is _Stomoxys calcitrans_, usually known as the biting housefly, but +sometimes called the stable fly because of its great abundance about +horses and cattle. The stable fly may be recognized by the fact that it +holds its head higher than the housefly, but Howard says that “the best +way to distinguish between the two flies is to allow them to walk over +your hand; if it bites it is _Stomoxys_; if it does not it is probably +the housefly.” The housefly has no mouthparts adapted for biting, but +the stable fly is provided with a sharp awl-like proboscis, and sucks +the blood from its victims. It is a great lover of direct sunshine, +and, when not engaged about cattle and horses may be seen sunning +itself on walls and fences. In damp weather it invades houses and +verandas, and it is then that the silk-clad ankles suffer. This habit +has given rise to the popular idea that houseflies bite just before a +storm. The bite is painful at the moment, but there is no subsequent +swelling or irritation; the puncture, according to Howard, does not +seem to be poisonous to man, and aside from the pain given it is far +less dangerous than a mosquito bite. + +The life history of _Stomoxys_ has been worked out by Newstead, who +found that the creamy-white eggs are laid about sixty at a time in +irregular clusters, usually in manure of some kind, but frequently +in piles of decaying grass or straw. Howard reared the fly from cow +manure, and says that the egg usually hatches in two or three days. +“The larva need not be described,” he says, “because it is so similar +to that of the housefly.” Newstead found that in this stage they lived +from fourteen to twenty-one days, but that the absence of excessive +moisture and the admission of a little light materially retarded +development, which then extended over a period of thirty-one to +seventy-eight days. In the puparium the insect remained from nine to +thirteen days. The development of the species is therefore much slower +than that of the true housefly. It is Newstead’s opinion that the +winter is passed chiefly in the pupal condition. + +The stable fly is considered by Austern and others to distribute +various diseases among cattle, but is probably not dangerous to +man. Brues remarks that it was once “thought to be a carrier of +poliomyelitis (infantile paralysis) but it now seems probable that +such is not the case.” Howard says, “I judge from the fact that it is +attracted to human excreta that it may become a carrier of intestinal +diseases,” but it has never been proved to be more than an accidental +agent in this matter. + +Bishop reports a great outbreak of this pest in Texas, where they were +found breeding in straw stacks, and caused serious injury to cattle and +horses. A similar case recorded by Lucian Iches of Santa Fe, Argentina, +is described by Howard: “The biting flies swarmed on a large estate +in almost incredible numbers. The cattle were driven nearly crazy by +them. Certain valuable Durham bulls which were observed were covered +with the flies. They had lost their hair in large spots and the skin +was cracking. Monsieur Iches naturally sought at once for the principal +breeding places of the flies, and found them to be in the stacks +of debris from the threshing of wheat and flax. Larvae and puparia +were found by the millions in the lower portions of these piles of +straw, where some fermentation had already begun. The sensible measure +which he recommended was to have this debris burnt within forty-eight +hours after the completion of the threshing, the ashes being used for +fertilizing purposes. It turned out that there was an old provincial +law in the province of Santa Fe ordering the burning of all debris +after threshing, but it had not been carried out during recent years, +and therefore the _Stomoxys_ multiplied until this veritable plague +ensued.” + +Another plague of stable flies occurred some years ago in Oregon, but +the life history was not known there and the breeding places were never +found. The severity of the pest’s bite is remarked by Osborne: “It +causes a great deal of annoyance to horses, cattle and other domestic +animals, and is frequently very troublesome to people working in places +where it abounds: Its bite is not poisonous and aside from the pain +given and the possibility of its disseminating disease, it is less +injurious than some other members of the group. When abundant, however, +the annoyance may be very great.” Bold describes the pitiable condition +of cattle bitten by the stable fly: “In some of the severe cases the +joints were so much swollen that the poor animals could not bend their +legs to lie down; and in them the inflammation rose so high as to +cause the loss of the outer skin and hair.” + +The cluster fly (_Pollenia rudis_) is a little larger than the +housefly, and appears longer because the wings overlap in such a +fashion as to make the body appear very slender. The thorax bears +many short, yellow hairs, and the grayish abdomen inclines to be +iridescent. During the Summer this fly lives upon flowers and fruits, +and does not come near houses, but the adults seek sheltered places +in the Fall, and spend the Winter in large groups or clusters--hence +the name. When the clustering process happens to take place within a +human habitation the flies become a nuisance. Howard quotes one of his +correspondents from Illinois: “They seem to prefer to occupy the rooms +on the north side of the house and those that are used but little. +They gather in large bunches in the corners and along the edges of the +ceiling. They cannot be driven out like other flies, but must be killed +outright to get rid of them, and when you mash them the odor is like +that of honey. We have tried nearly everything that was recommended to +us, with no effect. It seems impossible to get rid of them, or to keep +them out of the house, for they crawl in through the smallest places in +the windows.” + +They enter one by one through small cracks or crevices, and, as one of +Herrick’s correspondents writes, “screens and other devices which work +perfectly in excluding the ordinary fly are useless in keeping these +out.” W. H. Dall, describing the pest at Geneva, New York, states that +“people soon learned to look everywhere; in beds, in pillow-slips, +under table covers, behind pictures, in wardrobes, nestled in bonnets +and hats, under the edge of carpets, etc.” + +We are singularly ignorant of the life history of this insect. Macquart +and Desvoidy have found _Pollenia_ larvae in manure, and the Bureau +of Entomology people reared a single specimen from cow dung. Keilin, +however, claims to have discovered the maggot living as a parasite +in certain species of earth-worms. It is said that the adults are +particularly susceptible to the same fungous diseases which attack the +housefly. + +The lesser housefly (_Homalomyia canicularis_) is generally regarded by +laymen as an immature specimen of the common housefly, but is really +a distinct species, belonging to a different family altogether. The +housefly, or any other fly for that matter, does not grow at all in the +winged state--the newly emerged adult is quite as large as it will ever +be. The _Homalomyia_ maggot is very different from that of the ordinary +housefly; it measures only about one-fifth of an inch in length, and is +covered with spiny processes, to which the dirt clings and gives the +creature a mottled, dirty appearance. They develop in various kinds of +garbage and manure, being especially partial to human excrement. Hewitt +has found them very abundant in privies, and Herrick remarks that “this +habit of breeding in excreta of various kinds makes the flies dangerous +inhabitants of our rooms. They may act as conveyers of disease germs +quite as readily as the housefly. They are rapid breeders, for a +generation may be produced in two weeks in hot weather.” + +The blue-bottle fly (_Calliphora erythrocephala_) has a dull-colored +thorax and a dark metallic blue abdomen. It is sometimes known as the +blow-fly, and lays its eggs on meat and dead animals, or even in sores +upon living creatures. A single female has been known to lay more than +six hundred eggs, and Hewitt says that twenty-three days is sufficient +to produce a generation. The blow-fly ordinarily lives in the open air, +but occasionally gets into houses, particularly in stormy weather. +Herrick remarks that “it has been found frequenting human feces and +for this reason may be suspected of bearing intestinal bacteria, thus +making it a fly to be dreaded.” + +The so-called cheese fly (_Prophila casei_) is a little shiny black +fellow which develops in cheese, bacon, ham, chipped beef and the like. +The larva is known as the cheese skipper because of its remarkable +agility. Howard says that it will sometimes jump three or four inches, +and I have myself seen these vigorous little maggots, stimulated by +the heating of their home in a piece of Southern bacon, leap clear out +of the frying pan into the camp fire. The cheese fly is not native to +America and was probably imported in an early shipment of Swiss cheese. +The insect is not particularly dangerous, but as Howard says “it is +well to remember that not only has it been reared from dead bodies, but +that it is also attracted to excreta of all kinds.” + +The moth fly (_Psychoda minuta_) is a very fragile little insect whose +broad wings are hairy like those of a moth. It is very common among +weeds, clinging to the under surfaces of leaves, and often enters +houses, passing easily through the ordinary fly screen. According to +Herrick, “the larvae of some of these flies live in cow dung, others in +decaying vegetation, while some live in water, especially sewage water +or drain water from kitchens. We have often seen hundreds of these +moth flies among the weeds overhanging a ditch carrying the drainage +water from a kitchen. We have also seen them in abundance along ditches +carrying sewage water from houses. In the first-mentioned instance they +were always present on the window panes of the kitchen, readily passing +through the ordinary wire screen. Judging them from the places in which +they breed, we would consider them unwelcome guests in our houses.” The +moth flies of Southern Europe bite human beings, and are carriers for a +disease called phlebotomus fever, but the species so far identified in +the United States probably do no particular damage. + +The tsetse fly (_Glossina palpalis_), the sole distributor of the +deadly sleeping sickness which has decimated the native population +of equatorial Africa, is a near relative of our common housefly. The +reproduction of the tsetse fly is very different from that of most +insects, however. According to Brues, “the female does not deposit her +eggs, but a single one develops to the fully grown larval condition +before being deposited. This larva soon pupates in the shade beneath +the brush bordering the water where it has been dropped by the parent +fly, and later emerges in the winged adult condition. The pupae +requires such moist shade, and it is apparently for this reason alone +that the flies never occur away from the immediate vicinity of the +water. As a result of their method of development, the tsetse flies +do not multiply rapidly, and even under favorable conditions only one +larva is produced in a ten-day period.... It was thought at first +that by moving all the natives back from the edges of the water, the +flies thus left without opportunities for reinfection, would become +free from trypanosomes (the organisms causing the disease) and that +by isolating and treating cases of the disease in fly-free areas it +would be possible to eliminate them entirely. In conjunction with +this, the cutting of brush, especially about boat landings and +watering places, has been practiced as far as possible. Contrary to +expectations, it has been found that even after three or four years, +infected flies still occur along the uninhabited shores. This led to +experimentation upon animals and it is now known that various wild +antelopes as well as certain domestic animals may act as reservoirs for +the virus of sleeping sickness, which may thus persist in the complete +absence of any human subjects. As a result of this discovery the great +difficulties of combating the disease ... have been vastly increased.” + + + + +MOSQUITOES AND DISEASE + + +The mosquito is nothing more than a small, slender fly, very similar +to the housefly in every essential detail of its structure. There +are about sixty species and varieties in America, but the three +most common and important species are: the ordinary house mosquito +(_Culex pipiens_) which does not carry disease, the malarial mosquito +(_Anopheles quadrimaculatus_) which disseminates malaria, and the tiger +mosquito (_Aedes calopus_) which is a carrier of yellow fever. + +The common house mosquito has perhaps no equal as a persistent and +universally damned destroyer of human tranquility. Heartily detested +everywhere, even by entomologists, no serious studies of the life +history were made until comparatively recent years. The female deposits +her eggs upon the surface of still water in boat-shaped masses, each +mass containing from fifty to two hundred eggs. The floating egg-mass +is always large enough to be seen with the naked eye, and often +measures a quarter of an inch in length. The eggs usually hatch in two +or three days, and the larva is the well-known wiggler which swims with +a peculiar jerky motion in every rain-barrel and roadside pool in the +country. The wiggler breathes through a tube near the caudal end of +its body, and usually hangs head downward at the surface of the water, +with the tip of the breathing tube in contact with the air. The food +consists largely of minute organisms collected by two vibrating tufts +of hair about the mouth. After a week or so of this wriggling life, the +larva is transformed into another stage called the pupa, which has a +larger head and thorax, and rides differently in the water because the +breathing tubes have shifted to the upper part of the body. In five or +six days more the skin of the pupa splits open and the adult mosquito +slowly emerges. It usually rests quietly on the floating pupa-skin for +a few moments, and then, as soon as its wings are sufficiently dried, +flies away in search of food and mates. + +The male _Culex_ is much handsomer than the female, being provided +with large plume-like feelers or antennae, by which he may be easily +recognized. Another important sex-difference is that the _male doesn’t +bite_, but lives by sucking the nectar of flowers, like a bee. The +female of the species is deadlier than the male, even among mosquitoes, +and it is the female that does the blood-sucking. The mosquito’s beak +consists of several sharp lances inside a sheath, the whole apparatus +admirably adapted to pierce the human skin and transfer human blood to +the stomach of the mosquito. Incidentally some poisonous substance, +probably a salivary secretion, flows into the wound and produces more +or less inflammation and swelling. The _Culex_ or house mosquito, so +far as is known, does not transmit any disease to human beings--it is +detested only because of the pain which follows its bites, and its +intolerable buzzing. + +The malarial mosquito (_Anopheles quadrimaculatus_) deposits its eggs +singly on the surface of the water, never in rafts like those of the +house mosquito. The eggs are very seldom found in barrels or tubs about +houses--the _Anopheles_ prefers ditches, or creeks, or the shallows of +slowly flowing rivers. The malarial larvae do not hang head downward at +the surface as the _Culex_ wigglers do, but lie flat just beneath the +surface film, and may be identified by this characteristic horizontal +position. The _Anopheles_ pupa does not differ greatly in appearance +from that of the house mosquito. The adult is somewhat larger than +_Culex_, and the wings are gray-spotted instead of clear. Another +important difference is this: _Culex_ alights and rests with its body +parallel to the surface which supports it, while _Anopheles_ rests with +its body at an angle--head down, tail up. Herrick says that he has seen +them “clinging to the ceiling of a horse stall by their four front +legs, with their bodies hanging almost straight downward.” + +It has been known for a long time that malaria, otherwise known as +ague, or chills-and-fever, was connected in some way with stagnant +water. It was obvious enough to everybody that the disease was most +prevalent in low, swampy regions, and most people regarded it as a +result of poisonous gases which somehow arose from the surface of the +waters. The word _malaria_ means _bad air_. It was later discovered +that the real cause of the disease is a microscopic bit of jelly-like +protoplasm--a protozoan parasite which lives in the red cells of the +blood. Brues tells us that “the protozoan blood parasites which cause +malaria were first demonstrated many years ago, in 1880, by a French +surgeon, Laveran, who discovered them in the blood of persons suffering +from malaria. Five years later an Italian, Golgi, distinguished +three kinds, each associated with one of the more familiar types of +malaria. They were found to go through a regular life cycle in the red +blood corpuscles and, from analogy with other known protozoa, it was +suspected that in addition to their non-sexual generations in the human +blood there must be a sexual development in some cold-blooded animal. +Manson was led to suspect that some insect might be the secondary +host and, working on this hypothesis, Ross in India first found the +malarial parasites in a certain kind of mosquito in 1898. He had +worked for nearly three years with a common mosquito belonging to the +genus _Culex_ without result, but finally in a mosquito of the genus +_Anopheles_ was able to trace the development of the parasite. His +epoch-making discovery has since been amply confirmed and extended by +experimental proof until we now know that the various types of malarial +blood parasites complete their life cycles in anopheline mosquitoes, +the latter acting as the sole carriers of the disease.” + +Malaria, then, is acquired in one way only, and that is through the +bite of the malarial mosquito. A mosquito sucks a little blood from a +malarial patient, this blood containing some of the protozoan germs +which are the immediate cause of the disease. In the stomach of the +mosquito the parasites reproduce sexually, penetrate the stomach +walls, and proceed finally to the salivary glands, from which position +they are injected into the blood of the next victim of the mosquito’s +blood-lust. The parasites reproduce asexually in the man’s red blood +corpuscles, and then burst out by millions into the liquid part of the +blood. This happens simultaneously in all parts of the body, and the +patient is shaken by the chills characteristic of the disease. Some +varieties of the germs reproduce every two days, producing what is +known as tertian fever; other types form spores every three days, and +the resulting disturbance is known as quartan fever. After a while male +and female germs appear in the patient’s blood plasma, but these never +develop unless the sufferer is bitten by another mosquito. When this +occurs, the sexual germs pass into the mosquito’s stomach, reproduce +sexually, and are distributed as described above. Another man bitten, +more non-sexual reproduction, more chills and fever, and so on _ad +infinitum_. + +A healthy person may, of course, be bitten by _Anopheles_ and have +a great many malarial germs in his body without developing malarial +fever, as they sometimes lie dormant in the blood without reproducing +at all. Ross has estimated that “something like a quarter of a billion +of them must be present to produce fever.” The more infected mosquitoes +that bite one, the larger the number of germs that will be introduced, +and the more severe the disease. The essential result of all the +investigations is concisely stated by Herrick: “Malaria is caused by a +minute animal parasite that lives within the red blood corpuscles of +human beings. The parasite destroys millions of the red blood cells +that are so necessary to life, and, in addition, secretes certain +poisonous substances known as toxins, which lodge in various parts of +the body.... Since this parasite lives only in man and the mosquito, +it can get from one person to another only through the agency of these +insects. In other words, a person once free from the malarial parasite +will remain free just so long as the bites of certain species of +mosquitoes can be avoided.” One acquires malaria in one way only, and +that is by being bitten by _Anopheles_ mosquitoes. + +[Illustration: + + Fig. II. Malaria and its Carrier. A, the malarial mosquito, + _Anopheles quadrimaculatus_. B, chart showing the seasonal prevalence + of malaria in the United States. +] + +The tiger mosquito (_Aedes calopus_) is not native to the United +States, but has been introduced from the tropics. Today, however, it +is widely distributed in the Southern States, and has been found as +far north as New York. The eggs are laid singly or in small groups in +stagnant water, and hatch in from twelve hours to three or four days. +The larval life lasts about nine days, and the larvae are much more +active than the other mosquito wigglers. The tiger mosquito is not +often found in the country, but always near human dwellings, and it +prefers to deposit its eggs about houses, in vessels containing only a +little water--tubs, cisterns, rain barrels, old tin cans and the like. +The pupa state lasts only about two days, and the whole development +from egg to adult is sometimes passed in less than a fortnight. The +adult is considerably smaller than the other mosquitoes described here, +and is conspicuous for its white banded legs, and the prominent white +stripes on the thorax. + +In 1881 a man named Carlos Finlay claimed that yellow fever was +transmitted by mosquitoes, but nobody paid any serious attention +to this novel theory, as everybody thought yellow fever was highly +contagious--carried about in the clothing like smallpox. In 1900 a +commission of United States army officers--Drs. Reed, Carroll, Lazear +and Agramonte--went to Cuba to make an experimental study of the +situation there. The procedure and results are concisely summarized by +Herrick: + +“In a field near Quemado, Cuba, this commission of surgeons erected +a small wooden building tightly ceiled and with the windows and doors +closely screened so that no mosquitoes could enter. In this house, +during a total of sixty-three days, seven non-immune men were kept. +These men slept in beds furnished with the unwashed pillow-slips, +sheets, and blankets that had previously been used on the beds of +genuine yellow fever patients in Havana and elsewhere. This bedding was +actually stained with the excretions of the fever patients. Neither +during that time nor subsequently did one of these seven men develop +a case of yellow fever. This indicated to the surgeons, beyond much +question, that yellow fever is not carried in clothing, as had always +been held. + +“Another house was built in this same field and divided into two +rooms by means of a wire screen extending from floor to ceiling. The +doors and windows of each room were closely screened with fine wire +netting so that no mosquitoes could enter. All bedding and material +carried into the rooms were disinfected by steam, which precluded any +possibility of the yellow fever germ being present in the bedding or +clothing. + +“In one of the rooms, mosquitoes of a certain kind that had previously +bitten patients sick with yellow fever were placed. In the other room +none were allowed. Non-immune men were placed in both rooms. Of those +in the room containing no mosquitoes, not one had yellow fever. Of +those in the other room that were bitten by the infected mosquitoes, +six out of seven developed cases of genuine yellow fever. This +indicated beyond much question that mosquitoes were transmitters of +this disease. + +“These experiments have been extended and duplicated many times with +the same results, so that we are justified in believing that a certain +mosquito known as _Aedes calopus_ is the sole and only agent in the +transmission of yellow fever.” + +Dr. Lazear died from fever during the course of the experiments--a true +martyr of medical science--and Dr. Carroll came very near losing his +life also, following the bite of an experimentally infected mosquito. +Among other things, it was discovered that a mosquito may bite a +person suffering from yellow fever without becoming infected, unless +the bite occurs during the first three or four days of illness--later +than this the poison is not present in the blood. Another interesting +fact is that the _Aedes_ cannot infect anyone until at least twelve +days after it has received the virus from a sufferer, but after this +period it remains infected for a long time, and may give the disease to +a large number of people. + +The actual cause of yellow fever is as yet undiscovered. As Herrick +says, “it is either too small to be seen with any lens now made or +it inhabits some organs of the body not suspected, or its habits are +entirely different from any other parasite with which we are familiar. +In any case the germ has eluded all efforts to locate it and scientists +are still ignorant regarding its real nature, habits, and appearance.” +It has been supposed that the yellow fever organism is similar to the +protozoan which produces malaria, but we do not know. Very little of +importance has been learned about the disease or the mosquito since +the Cuba commission in 1900, but wonderful progress has been made in +the application of such information as we have. By 1902 Havana was +entirely free from the yellow fever, and Rio de Janeiro, which had been +a fever-hell for many years, eliminated the disease entirely after a +six-year fight with the mosquitoes. In the Panama Canal Zone an army +surgeon named Gorgas was very successful in combating both yellow +fever and malaria. Although the United States has never suffered as +the tropical countries have, there have been numerous epidemics, the +last of which broke out in New Orleans in 1905. Vigorous anti-mosquito +campaigns were waged and the plague stamped out in a short time. The +tiger mosquito is still common all over the South, but there are no +yellow fever patients for them to bite. When a case does appear--some +sailor from the tropics, usually--he is seized by the Public Health +Service people and placed where no mosquito can get at him, and thus +it has not been necessary to wage a general exterminative war on the +yellow fever mosquito. + +When the situation gets out of hand vigorous measures for the temporary +and local eradication of the insect are of course necessary. As Brues +says: “The success of this campaign has undoubtedly sounded the death +knell of the yellow fever epidemic and panic in the United States, for +New Orleans has amply demonstrated what may be accomplished in the +control of an epidemic by an efficient group of workers backed by a +sympathetic public and supplied with reasonable funds. Even in parts +of the tropics where it persists throughout the year, it is being +rapidly and permanently eliminated. Indeed, it bids fair to be the +first disease actually to become extinct as a direct result of human +discovery and applied science.” + +There is, so far as is known, no satisfactory method of destroying +mosquitoes in the adult state, so that in the war against this pest we +must direct our efforts against the eggs and young. Herrick tells us +that “the methods taken to destroy mosquitoes fall into three distinct +classes; namely, the draining of bodies of water liable to contain eggs +and wrigglers, the application of oil to bodies of water that cannot +be drained and the introduction of fish into pools that cannot be +drained or oiled.” + +Probably the best way to rid one’s immediate vicinity of mosquitoes +is to drain all marshes, pools and open receptacles. The drying up of +a few acres of swamp land may cause a marked fall in the death-rate +of an entire neighborhood, particularly in regions where malaria is +prevalent. The exposure of open tanks, reservoirs and barrels in which +stagnant water stands is no less than criminal in some parts of the +South. + +Very often, for economic reasons, it is not practical to drain a +swamp or to eliminate open sewage ditches. In such cases we may take +advantage of the fact that the larvae of mosquitoes do not breathe by +gills, but are forced to come to the top for air. If ordinary kerosene +oil is sprayed upon the surface of the water, it spreads to form a +thin film which the larva cannot penetrate with their breathing tubes, +and so are drowned. The kerosene also destroys the floating eggs, and +kills the female mosquitoes as fast as they attempt to deposit. Crude +petroleum has been used instead of kerosene, but it does not spread as +well, and is very little cheaper. According to Herrick, one ounce of +kerosene is enough for fifteen square feet of water surface, and half a +teacupful is plenty for a barrel of water. The most convenient way to +apply the oil to small pools and ditches is by means of a five-gallon +tank carried knapsack fashion, with a short hose and nozzle. As the +entire development of the mosquito from egg to laying female seldom +requires more than eighteen or twenty days, it is best to use the oil +once every two weeks during the mosquito season. It would seem that +an easier way to get kerosene into the sewage ditches would be simply +to pour it into the water closet, and this has proven successful in +cases where there is little or no current; on the whole, however, the +surface-spraying system is best. + +Ornamental ponds and pools cannot be drained or sprayed with oil, and +the same may be said of artificial ponds where domestic animals drink. +In these cases the mosquito pest may be mitigated by introducing fish +or other small creatures which feed upon the larvae. In Japan, and +more recently in other countries, the goldfish has been found very +satisfactory for this purpose. Various species of shiners, sunfish and +top minnows have also been used. W. P. Seal, who has given a great +deal of attention to this phase of the mosquito problem, states his +results as follows: “The writer has come to the conclusion, after +many experiments in small ponds, that a combination of the goldfish, +which is ornamental and useful in the open water, the roach or shiner, +which is a very active species, two small species of sunfish, which +live among plants, and the top minnow would probably prove to be more +effective in preventing mosquitoes breeding than any other fishes.” + +Vernon Kellogg, Tillyard and others have studied the habits of +dragonflies in this connection, and the latter particularly has +emphasized their value as destroyers of mosquito larvae. He saw +a single dragonfly larva eat sixty wrigglers in ten minutes, and +captured an adult dragonfly which had over a hundred mosquitoes in +its mouth--so many that the mouth could not be closed. “I believe that +a successful checking of the mosquito pest in the ornamental waters +of parks and gardens could be readily obtained by the introduction of +dragonflies whose larvae, as well as the adults, would prey upon the +nuisance.” + +The use of wire screens to exclude flies and mosquitoes from dwellings +is now well-nigh universal in most parts of the United States, although +there are still many rural communities in the South in which it +appears to be quite unknown. To keep out ordinary mosquitoes the wire +should have at least fourteen meshes to the inch, and the yellow fever +mosquito will pass through any screen which has less than eighteen +meshes. It is practically impossible to fit screens and frames well +enough to exclude all mosquitoes, but it is certainly better to contend +with a few stray mosquitoes in a screened house than to do battle with +the myriads of pests which swarm into an unscreened domicile. The +fewer the bites one receives, the fewer the chances of being bitten by +an infected mosquito; the fewer infected bites, the less severe the +resulting illness will be. + +In many Southern cities the use of bed nets of bobbinet or mosquito bar +has now become quite general. There is usually a kind of wire frame +over the bed, and the net is sometimes tucked under the mattress all +round, while in other cases it is long enough to reach the floor on all +sides. Many travelers who must visit small towns, where the hotel bed +nets are lacking or unsatisfactory, carry their own nets, and set them +up every night to suit their fancy. Dr. Ross says: “Perhaps our first +and best defense against malaria lies in the habitual and scrupulous +use of mosquito nets at night.... The first care of the resident in the +tropics, of the traveler, the sportsman, the soldier, the miner, the +clerk, should be for his mosquito net. Wherever he lives, wherever he +goes, he should see that his mosquito net is with him, that it is in +good order, and that it is properly arranged at bedtime.” + +There are several chemical substances used in driving mosquitoes out +of houses. One may rid a room of mosquitoes by the fumes of burning +sulphur, but the gas often discolors articles painted with lead +paint, and tarnishes gilt furniture and brass bedsteads. A vegetable +powder sold as pyrethrum, buhach, or Persian insect powder is made of +chrysanthemums, and is fairly effective when scattered about or blown +into cracks and crevices. It may also be burned as a smudge, but the +fumes are not as effective as those of sulphur. Many of the mosquitoes +fall to the floor in a stupor, and must be gathered up and burned, as +otherwise they will revive in an hour or so. Another fumigant much in +favor in New Orleans is a mixture of carbolic acid and gum camphor, +and is known as culicide. A heavy reddish liquid, it is evaporated by +heating slightly over a gas burner or alcohol lamp. The mixture is +inflammable but not explosive, and the fumes are not dangerous to human +life. + +Hunters and campers often smear their hands and faces with various +substances supposed to discourage mosquitoes, oil of citronella being +one of the most popular. Camphor, cedar oil, kerosene and mixtures of +these substances in various proportions are also used, besides several +patented smudges and ointments. I have tried several of these, but +found them unsatisfactory. Tobacco-smoke helps a little sometimes, and +is at least free from the unpleasant and even nauseating odors of the +other mosquito repellants. + + + + +LIFE AMONG THE BEDBUGS + + +The bedbug (_Cimex lectularius_) has been known to man for a long +time, and has probably, as Herrick remarks, “been man’s bedfellow as +long as man has slept in beds,” if not longer. The ancient Romans +were intimately acquainted with this insect, and Pliny recommends a +mixture of macerated bedbugs in water as a cure for snake bites. It +is common in all parts of the civilized world, and doubtless came to +America with our sturdy fathers--even the Mayflower probably carried +a full cargo of bedbugs. Like its relative the stink bug, _Cimex_ has +a peculiar odor which is quite noticeable in small rooms where the +insects are unusually abundant. The full-grown bedbug is a flat-bodied, +mahogany-colored creature, with mouthparts admirably adapted to +blood-sucking. It lives in beds, window casings, cracks in floors, +etc., or in any article of furniture which affords a crevice large +enough to contain it. What we know about the insect’s life history +is mainly due to Marlatt, who did his work in 1896, and to Girault, +who carried out some further investigations some ten years later. The +eggs are very small, white and oval, and are, according to Herrick, +“laid in batches of varying numbers in cracks and crevices in the +bedsteads or other places where the bedbugs happen to be. The number of +eggs deposited by a single female is not known. Southall, Riley, and +others have made the common statement, probably not based on actual +observation, that each female lays about four batches of fifty each +during the season. Girault actually succeeded in obtaining 111 eggs +from one well-fed female between June 17 and August 19. How many she +had deposited previous to confinement for the experiment he was, of +course, unable to say. Girault’s experience with this one bug indicates +that the females may continue to lay eggs at different periods +throughout the breeding season and that there is only one generation a +year.” + +The eggs hatch in about ten days, and the young bugs appear very much +like their parents--bedbugs do not pass through larva and pupa stages +like flies and mosquitoes. Bedbugs probably eat nothing but blood, +and a young individual, if properly supplied with this food, reaches +maturity in about six weeks, shedding their skins at least five times +during the period of growth. It is said that the bug feeds but once +between moults; if this is true the occupant of the bed must suffer +at least five bites in order to rear a single bedbug to maturity. +Bugs very much like _Cimex_ are found upon swallows, chimney swifts, +pigeons and martins, and many people believe that genuine bedbugs +are distributed by these birds, but this is probably not the case. +True bedbugs have never been found upon them, and although the “bird +bedbugs” are occasionally found in houses they do not seem to enter +beds and bite human beings. Bedbugs have, however, been found in +chicken houses, where they presumably bite chickens, so that there +is nothing inherently unreasonable in the view that they may be +distributed by birds. + +The bedbug almost invariably lies hidden during the day, or as long as +there is a bright light in the room. As soon as the light is turned off +they sally forth to attack an exposed portion of the sleeper’s body. +It seems that they are particularly likely to be secreted about the +pillow, and as soon as the room is dark hit upon the neck as the most +desirable and accessible part of the victim’s anatomy. Only one who has +had personal experience in these matters can appreciate the vigor of +the onslaught, and the astounding rapidity with which the enemy whisks +out of sight the moment the light is flashed on. The bedbug’s bite is +not poisonous, and the pain is probably due only to the puncture, but +this is sufficient to cause considerable irritation and swelling. + +Elie Metschnikoff, the author of that fascinating book entitled _The +Nature of Man_, was the first to call attention to the bedbug’s +possibilities as a carrier of disease germs. Bedbugs have been made, +under laboratory conditions, to transmit typhoid and other fevers, +and a tropical disease called _kala-azar_, but it has never been +demonstrated that the bugs actually do, under ordinary conditions, +play any part in the diffusion of these diseases. “Many writers and +experimenters,” writes Herrick, “have labored hard to prove this insect +guilty of graver offenses than that of simply stealing blood from human +hosts. The most they have been able to do so far, however, is to show +that in one case, at least, the bite of the bedbug formed a starting +point for a case of bubonic plague. As a matter of fact, this is really +a stronger indictment against the bedbug than, at first thought, might +appear. The sores resulting from bedbug bites offer ideal points of +entrance for disease-producing organisms and are a source of real +danger. Actual and definite proof that the bedbug transmits disease +is very difficult to obtain, but suspicion points strongly in that +direction.... It is extremely desirable to avoid the bites of this +insect if possible, especially in hotels where beds are occupied by so +many different people; but this is very hard to do, in fact, almost +impossible if one travels much.” + +Luckily the bedbug is wingless, and therefore much easier to control +than winged pests like the fly and mosquito. If _Cimex_ were able to +fly there would be no keeping him out, as the newly hatched young could +pass through practically any sort of screen. The use of metal bedsteads +puts the bugs at a disadvantage because they afford fewer cracks and +crevices than those built of wood. Boiling water poured into the +crevices kills both eggs and bugs, but a more convenient method is to +use an oil can or squirt-gun filled with gasoline, kerosene, turpentine +or alcohol. The easiest way to rid a room completely of insects is to +fumigate with hydrocyanic acid gas, made by pouring dilute sulphuric +acid on potassium cyanide. This gas kills every living creature in +the room, but it is dangerous in the hands of careless or thoughtless +persons. + + + + +LICE, CRABS AND COOTIES + + +Lice have been associated with human beings as far back as our +historical records go, and are mentioned in the writings of Aristotle, +Herodotus and other ancient writers. Ordinarily cleanly and +well-dressed people today would be horrified to find lice about their +persons, as they are now confined to soldiers and others who do not +keep their bodies and clothing clean, but a few hundred years ago, +when everybody was dirty, they thought nothing of it. Samuel Pepys, an +English diarist of the seventeenth century, made the following laconic +entry in 1668: “Up betimes, finding our beds good, but lousy, which did +make us merry,” and there are many other matter-of-fact references to +these vermin in the literature of the period. + +There are three common species, but they are all essentially alike in +structure, being small, wingless and provided with piercing and sucking +mouthparts. Schiödte describes the behavior of a louse on the back of +his hand: “Scarcely does the abominable little monster feel the heat +of the skin before it lays aside its former disheartened attitude, +and begins to feel at ease, its antennae oscillate for joy, and it +stretches all six legs complacently out from the body. But though the +pleasure and surprise at the sudden transportation into congenial +surroundings for the first moment eclipse everything else, hunger +soon asserts its claim, sharpened as it is by the long fast, which +has rendered its stomach and intestines quite transparent. The animal +raises itself on its legs, walks a few steps, seeking and feeling its +way with its antennae, while we follow it with a magnifier. Presently +it stops, draws in its legs a little, arches its back, bends the head +down toward the skin at an oblique angle, while it probes a small dark +and narrow organ repeatedly forward, and draws it back through the fore +end of the head; at last it stands still, with the point of the head +firmly abutted against the skin.” + +All three of our species are blood-suckers, and are strictly human +parasites, being found only occasionally upon the bodies of animals +other than man. It is said, however, that they are sometimes carried +about by flies. + +The head louse (_Pediculus capitis_) is usually found among the hairs +on the head, occurring elsewhere only occasionally. The female is about +one-twelfth of an inch long, while the male is only about one-half +as large; both sexes are grayish in color, but it is said that this +varies with the color of the host. Herrick quotes Murray to the effect +that lice on West Africans are black, those on Chinese yellow, those +on Hindoos smoky brown, and so on. The eggs are fastened to the hairs +by a gelatinous secretion, and the female has been known to deposit at +least fifty eggs in the course of a week. The period of incubation is +usually five or six days, and the young louse reaches maturity in a +fortnight. The movements and bites of these creatures are irritating in +the extreme, and the sufferer is sure to scratch so incessantly that +the scalp is always in an inflamed condition. The head louse is not +known, however, to carry any disease-producing organism. + +The best way to get rid of the head louse, according to a circular +memorandum prepared under the direction of Surgeon General M. W. +Ireland, of the United States army, is to “clip the hair of the head +with a hair clipper and wash with a mixture of equal parts of kerosene +and vinegar. This should be followed in a few hours with a bath of soap +and hot water.... The hair should be caught in bags and burned. In +order to reduce the liability to infestation, the hair should be kept +close at all times.” Sulphur ointment may be used without sacrificing +the hair, but it is not so effective as the kerosene mixture. + +The body louse (_Pediculus corporis_), known also as the gray-back and +the cootie, is somewhat larger than the head louse, and is usually +of a dirty white color. These creatures dwell in the seams and folds +of clothing, and are therefore known to some writers as _Pediculus +vestimenti_. They are difficult to find and to dislodge, as they do +not often cling long to the skin, but retire to their hiding places +in the clothing as soon as their blood-sucking is done. The eggs are +laid in the seams and wrinkles of the clothing, that made of wool being +given the preference. When one has no opportunity to change or wash +one’s clothes the pests become so abundant as to be quite unbearable. +Soldiers, inmates of prison camps and such people are particularly +liable to be abundantly supplied with body lice; they may pass from one +person to another when the bodies are brought into actual contact, or +one may become infested by sleeping in louse-ridden beds. + +The Dutch scientist Leeuwenhoek, more than two hundred years ago, +carried out some experiments which are pleasantly reviewed by Herrick: +“Leeuwenhoek ... made an attempt to find out something definite about +the life history and rate of development of the body louse. He did not +believe the popular saying that a louse could become a grandfather in +twenty-four hours. At first he thought of hiring some person to act as +host for the lice. Later he changed his mind, overcame his own natural +aversion to these pests, and enclosed two large females within a fine +black stocking, the top of which he fastened tightly around his leg +above the knee. Here he allowed the two lice to live for six days and +obtain their sustenance from his leg. At the end of this period he +removed the stocking and found fifty eggs around one of the females +and forty eggs in another part of the stocking, evidently laid by the +second female, which, however, had escaped. He wore the stocking for +yet ten days, when on examination he found twenty-five young lice which +so disgusted him and dampened his enthusiasm that he threw the whole +thing into the street. Since Leeuwenhoek’s time the author is not aware +that any scientist has ever tried in the same way to study the life +history of these lice.” + +[Illustration: + + Fig. III. Three kinds of Lice. A, the head louse, _Pediculus + capitis_; B, the body louse, gray-back, or cootie (_Pediculus + corporis_); C. the crab or crab louse, _Pediculus pubis_. +] + +_Pediculus corporis_ is the only species of louse known to act as +a carrier of disease. Its connection with typhus and trench fever +is admirably described by Brues: “Typhus fever has been well-known +for many years and regarded as a disease characteristic of filthy +surroundings. During our own civil war it claimed many victims among +the inmates of army prisons, and has been endemic though not very +prevalent in many parts of the world in times of peace. Through the +researches of Ricketts and others we now know that typhus is spread +by the body louse and its epidemiology is at once made clear. When +it broke out in Serbia in severe epidemic form, a knowledge of the +method of its transmission made control possible, even under extremely +difficult and unfavorable circumstances. + +“Trench fever has attracted notice in the European war zones, to which +it appears to be restricted so far as present knowledge extends. +That it is a new disease is, however, without question an utterly +unwarranted assumption, for it has undoubtedly been brought to Europe +from some little-known quarter of the globe, unless it may have +previously existed in Europe which does not appear probable. During the +latter part of the war it was successively recognized as a distinct +disease, suspected of association with the louse, and soon proved +actually to be louse-borne. We now know that the disease is due to a +living microorganism, probably of such small size that it cannot be +recognized under the microscope. This virus is obtained by the lice +with their meal of blood taken from an infected person. At least five +days must elapse before the louse becomes capable of transmitting the +disease, indicating that the organism must undergo a development of +definite periodicity in the insect. If it is transferred to another +person its bite is not or only rarely infectious, but its excrement +contains the virus and if scratched into the skin, trench fever +develops. Typhus fever is a very dangerous disease with a quite high +death-rate, but trench fever is non-fatal and its importance in the war +zones has been due to its great prevalence and the fact that persons +afflicted with it are often incapacitated for long periods.” + +As body lice do not cling to the body except when actually biting, it +is a comparatively easy matter to get rid of them. One has only to +bathe while his clothing is being steamed or soaked in gasoline. The +United States Army set up delousing plants which were nothing but steam +sterilizes on a large scale, and they proved very satisfactory. + +The crab louse (_Pediculus pubis_) is short and stout-legged, whitish +on the back, with a distinct reddish cast about the legs. It usually +inhabits the hairy areas about the sex organs, clinging close against +the skin, but is not uncommon in the armpits, and has been found upon +practically every part of the body except the head. The eggs are +attached to the hairs, like those of the head louse; they hatch in less +than a week, and the young crab reproduces at an early age. This little +pest multiplies much more rapidly than either of the other species, +and is besides more easily transmitted from one person to another. +Although the usual means of communication is direct bodily contact, +as in the sexual embrace, it may be transmitted otherwise. The United +States Army memorandum informs us that “this insect is transmitted +mainly by contact in lodging houses, houses of prostitution, bathtubs, +and perhaps occasionally from toilet seats.... Although the crab louse +has not been shown to be a transmitter of disease, still it is very +annoying, and its presence is a reflection on a man’s cleanliness.... +The treatment for this condition is to shave the hair of the pubic +region, axillae, chest and legs. This should be followed by an +application of the kerosene and vinegar mixture, followed by a bath +with soap and warm water.” The usual treatment among civilians is the +application of a little mercurial or blue ointment. + + + + +OUR FRIEND THE COCKROACH + + +There are four common species of cockroaches in the United States, +only one of which is native to this country. The American cockroach +(_Periplaneta americana_) is the large winged species so common in +the Middle and Southwestern states. They devour nearly any sort of +food, and have been known to eat the corks out of bottles, while no +less an authority than Vernon Kellogg says that some sailors in San +Francisco sleep with gloves on to keep roaches from gnawing off their +finger-nails. The German roach (_Ectobia germanica_), known also as +the croton-bug, is common in the eastern part of the United States. It +is the smallest species we have, being seldom more than five-eighths of +an inch in length. For some reason or other these roaches are usually +found about water pipes, and are not common in small communities which +have no water systems. The Oriental cockroach (_Blatta orientalis_) is +common also in England, and came to America with the early colonists, +although it is supposed to have originated in Asia. It is larger and +stouter than the croton-bug, and is dark brown or black in color. The +males have short wings, but the females are wingless or practically so. +The Australian roach (_Periplaneta australasiae_) is very much like the +American variety, except for some yellow spots and bands on the thorax +and shoulders. It is less common than any of the others, being found +chiefly in the South. + +The life histories of all four species are essentially identical. The +eggs are not deposited singly, but in clusters enclosed in a horny +capsule, the end of which may often be seen projecting from the abdomen +of the female. The young roaches appear very much like their parents, +but do not reach maturity for several months. The flat bodies of +these insects allow them to crawl into small cracks in woodwork and +furniture, and they usually remain hidden during the day, coming out +at night to seek what they may devour. They are really scavengers, +and under certain conditions may be useful in this capacity, but +their omnivorous habits and the intolerable stench of their bodies and +excreta make them the bane of the careful housewife. + +“Cockroaches,” observes the indefatigable Herrick, “are among the +most difficult to control of the household pests. They are difficult +to reach because they are especially adapted with their thin, flat +bodies for hiding away in inaccessible cracks, crevices and crannies. +Moreover, they are wary and shy of all baits and traps. The croton-bug +is the most difficult of all to get rid of. It seems to display more +caution in avoiding traps and baits than most of the others, and as it +increases faster, it becomes much more abundant.” Several traps have +been devised and used with some measure of success, and roaches may +often be killed by feeding them plaster of paris mixed with flour, or +by exposing deep jars of stale beer, a delicacy in which they hasten to +drown themselves. Herrick quotes Washburn to the effect that powdered +borax scattered about the kitchen will clear a house of cockroaches. +The best way to completely rid a house of these pests is to fumigate +with hydrocyanic acid gas, made by pouring dilute sulphuric acid on +potassium cyanide. But this method, as I have pointed out elsewhere in +this booklet, is too dangerous for awkward or absent-minded people to +experiment with. + + + + +CHIGGERS, TICKS AND FLEAS + + +The chigger (_Leptus irritans_) is not a true insect, but the immature +form of a mite, related to the spiders. The eggs are laid upon the +ground in the Spring, and when the young chigger hatches it climbs up +a blade of grass and awaits the coming of some animal to which it can +attach itself. At this time it is a very small red creature, barely +large enough to be seen with the unaided eye. It clings to any moving +object which presents itself--usually some passing insect, but quite +frequently a bird or one of the higher animals. After having fed for a +time upon the blood and juices of its mount, the chigger drops off and +changes into the adult mite, which is not parasitic, but feeds largely +upon plant lice. + +Man’s contact with the chigger usually comes while walking through +the grass and weeds to which they cling. They cannot bear direct +sunlight, and are not common upon closely clipped lawns unless these +are very densely shaded. The tiny tormenter passes through the finest +of clothing--silk hosiery and underwear are no protection--and attaches +itself to the skin, sucking blood and setting up a severe irritation by +means of some poisonous secretion. The resultant itching is so intense +that one cannot resist the temptation to scratch the affected parts, +which may become infected and cause blood poisoning, and, according to +Hamilton, erysipelas. Although the chigger is not known to disseminate +any particular disease, it is an intolerable nuisance, and has +spoiled many a vacation in the South. + +[Illustration: + + Fig. IV. Some Common Cockroaches. A, Oriental cockroach (_Blatta + orientalis_), female. B, same, male. C, American cockroach + (_Periplaneta americana_). D, Australian cockroach (_Periplaneta + australasiae_). +] + +Some persons avoid chiggers by wearing high boots, others, sprinkle +sulphur in their stockings, while still others use various patent +preparations both before and after the act. My own experience is +that if, directly after coming in from the field, one changes to +chigger-free clothing and rubs whiskey or gasoline upon the parts +likely to be affected, the number of bites will be greatly decreased. +Dr. Vernon C. Allison treats the inflamed areas with potassium +permanganate, but I have had no satisfaction in the use of this remedy. + +The fever tick (_Dermacentor venustus_) is the carrier of the disease +known as Rocky Mountain spotted fever. This disease is now restricted +to the Northwestern states, most of the cases occurring in Idaho and +Montana. The life history of the tick is much like that of the chigger. +Hatched from eggs on the ground, the young seed tick mounts a tall +blade of grass or a weed and fastens upon the first animal which comes +along. Forcing the hooked sucking beak into the flesh of the host, it +sucks blood until it is full grown. Then it falls to the ground and +reproduces, dying soon after this duty is done. + +Brues describes the fever tick situation as follows: “The _Dermacentor_ +ticks occur abundantly on various small wild mammals in the younger +stages and as adults on domesticated animals, such as cattle, and from +these become transferred to man. It has been experimentally shown +that certain rodents are susceptible to the disease, and a tick thus +infected in the nymphal stage can retain the disease organism until +it becomes adult. It may then reach its human host through the medium +of domesticated animals such as cattle. It appears that this is the +ordinary way in which human cases have their origin, i. e., through the +bite of adult ticks, although the newly hatched _seed ticks_ derived +from eggs laid by infected mother ticks are known to contain the +organism also. + +“Although Rocky Mountain fever is of minor importance at the present, +it is feared that it may increase its range at any time, since other +ticks of wider distribution are apparently capable of acting as +carriers. Whether this may happen is by no means certain, however, +and the vigorous measures already undertaken to reduce the abundance +of ticks on domesticated animals will undoubtedly bear fruit in the +gradual reduction of this locally much-dreaded disease.” + +There are many other species of ticks in the United States, but their +life histories are all very similar. Several of them are believed to be +carriers for various diseases of cattle, but _Dermacentor venustus_ is +the only one known to distribute disease among human beings. The common +Southern cattle-tick (_Margaropus annulatus_) is the sole carrier of +the cattle disease known as Texas fever, which has caused a tremendous +pecuniary loss in several of the Gulf States. The protozoan parasite +which actually causes the trouble is called _Babesia bigemina_, and +Brues refers to the tick’s “becoming infected during its period of +engorgement when feeding on the blood of a diseased animal and then +transmitting the _Babesia_ through its eggs to the young ticks of the +next generation. These may feed on healthy animals the next season, +conveying to them the parasites that have been handed down from the +mother tick.” + +[Illustration: + + Fig. V. Chiggers and Ticks. A, young and adult chigger (_Leptus + irritans_) redrawn from Herrick. B, Rocky Mountain spotted fever + tick, (_Dermacentor venustus_), after Brues. Male at left, unengorged + female at right. +] + +Only two species of fleas are common in dwelling-houses in the United +States. One is the human flea (_Pulex irritans_) and the other is +_Ctenocephalus canis_, found almost universally upon cats and dogs. +One must not suppose, however, that human fleas bite humans only, and +that _Ctenocephalus_ confines its attention to dogs and cats; the human +flea does not scruple on certain occasions of good omen to attack dogs, +cats, rats and mice, while the various other species of fleas bite man +also whenever the spirit moves them. The adult flea lives entirely +upon the blood of its host, obtained through the admirable piercing +and sucking mouthparts. The human flea, according to Herrick, is so +bloodthirsty that it sucks regularly more blood than it can hold, and +the surplus is seen squirting out of the anus while the creature is +sucking more in at the mouth. + +The eggs are dropped almost anywhere, and the tiny white larvae develop +in cracks and crevices, feeding upon the organic matter in wood and +rubbish. The pupa is enclosed in a silken cocoon, and the adult may +appear in less than two weeks after the eggs are laid, although the +period is usually somewhat longer. + +Until comparatively recent years the flea was looked upon only as +a nuisance, but it has now been discovered that some species act as +agents in spreading bubonic plague, one of the most terrible scourges +known to human history. It appears that the plague is primarily a +rat-disease, and affects the human animal only incidentally. Outbreaks +of plague among human beings are always preceded by an epidemic +among the rats of the same region. The part placed by fleas in the +matter is stated by Brues as follows: “The relation of the flea to +the transmission of plague is due to the fact that rats are regularly +infested by fleas that may become infected with the bacillus of plague, +if it be present in the blood of the host upon which they are feeding. +These bacilli remain in a viable condition for some time in the gut +of the flea and may be transferred to a human subject bitten by an +infected flea. Thus, when a rat dies of plague, its fleas leave it to +search for a new host; if they attach themselves to a rat, that animal +is liable to infection, or if they feed upon a human being, as they +frequently do, the disease may become transferred to man.... The plague +bacilli (_Bacillus pestis_) appear only in fleas that have bitten +infected persons or rats twelve to twenty-six hours previous to death, +for after this time the bacilli do not occur in the blood. The vitality +and virulence of the bacilli are preserved for nearly a week at least +and sometimes fully a month; and there is actually an increase in their +number during the first few days. Infection from these insects may then +occur through their bites, if they contain extremely virulent bacilli, +but probably occurs more commonly by the insects being crushed _in +situ_ after they have punctured the skin.” + +From 300,000 to 400,000 cases of bubonic plague occur in India every +year, and nearly half of them terminate fatally. Comparatively few +cases have been reported from the United States in recent years, but +in various places, San Francisco for example, only the most vigorous +and persistent repressive warfare against rats and fleas have prevented +what might have been very serious outbreaks. + + + + +Transcriber’s Note: + +- Text that was in italics is enclosed by underscores (_italics_). + +- Illustrations were moved to the ends of the paragraphs in which +they originally appeared. Their original page numbers are in the list +of illustrations. The list of illustrations was not present in the +original text. + +- Inconsistencies in hyphenation have been standardized. + +- Minor punctuation errors have been changed without notice. + +- Spelling was retained as in the original except for the following +changes: + + Page 2: “Our Friend the Cochroach” to “Our Friend the Cockroach” + Page 3: “Europe. Picture Thomas Aquinus” to “Europe. Picture Thomas + Aquinas” + Page 8: “During the Spanish-American war” to “During the + Spanish-American War” + Page 13: “an epidemic which occured” to “an epidemic which occurred” + Page 13: “contended that purulent opthalmia” to “contended that + purulent ophthalmia” + Page 14: “is practically no opthalmia” to “is practically no ophthalmia” + Page 14: “spread of Egyptian opthalmia” to “spread of Egyptian + ophthalmia” + Page 16: “destroyed by the housekeper’s” to “destroyed by the + housekeeper’s” + Page 20: “walls and fences. in” to “walls and fences. In” + Page 20: “and verandas, and is” to “and verandas, and it is” + Page 21: “Lucian Iches of Sante” to “Lucian Iches of Santa” + Page 22: “the province of Sante” to “the province of Santa” + Page 23: “inclines to be irridescent” to “inclines to be iridescent” + Page 25: “this habit of breding” to “this habit of breeding” + Page 27: “a single one developes” to “a single one develops” + Page 32: “The parasites reproduce sexually” to “The parasites + reproduce asexually” + According to other passages in the text, the parasite that causes + malaria reproduces asexually in the human body and sexually in + mosquitoes. This typo was corrected to make the text internally + consistent. + Page 35: “a field near Quemados” to “a field near Quemado” + Page 37: “is that the Aedes” to “is that the _Aedes_” + Page 42: “or Persian insect power” to “or Persian insect powder” + Page 47: “writings of Aristotle, Heroditus” to “writings of + Aristotle, Herodotus” + Page 47: “ease, its antennae oscilate” to “ease, its antennae + oscillate” + Page 48: “antennae, while we followed” to “antennae, while we follow” + Page 49: “is not known, howeve” to “is not known, however” + Page 54: “application of the kerosense” to “application of the + kerosene” + Page 60: “cattle, but _Dermacentor venusta_” to “cattle, but + _Dermacentor venustus_” + Page 63: “years the flea looked” to “years the flea was looked” + +*** END OF THE PROJECT GUTENBERG EBOOK 79263 *** |