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diff --git a/77638-0.txt b/77638-0.txt new file mode 100644 index 0000000..8c0ba87 --- /dev/null +++ b/77638-0.txt @@ -0,0 +1,1449 @@ +*** START OF THE PROJECT GUTENBERG EBOOK 77638 *** + + + + +LITTLE BLUE BOOK NO. 833 +Edited by E. Haldeman-Julius + +Life Among +the Ants + +Vance Randolph + +Drawings by Peter Quinn + + +HALDEMAN-JULIUS COMPANY +GIRARD, KANSAS + + + + +Copyright, 1925, +Haldeman-Julius Company + + +PRINTED IN THE UNITED STATES OF AMERICA + + + + +CONTENTS + + +Chapter Page + + 1. Books About Ants 4 + + 2. The Ant’s Body 5 + + 3. Reproduction and Metamorphosis 12 + + 4. The Harvesting Ants 20 + + 5. The Mushroom Growers 25 + + 6. The Honey Ants 30 + + 7. The Legionary Ants 36 + + 8. The Red Slave Makers 46 + + 9. The Amazons and Their Slaves 51 + + 10. Dairies and Guests 54 + + + + +LIFE AMONG THE ANTS + + + + +CHAPTER I + +BOOKS ABOUT ANTS + + +There are many references to ants in the works of the ancients (Aesop, +Plutarch, Horace, Ovid and Pliny), and these were quoted and elaborated +by the mediaeval authors, but modern scientific investigation may be +said to begin with the nineteenth century. Since then an enormous +amount of work has been done by European scientists, but their papers +are scattered through the files of obscure scientific journals in a +great variety of continental languages, and are usually inaccessible or +useless to the American student who wishes to make a serious (but not +_too_ serious) study of ant life and behavior. + +The first general treatise in English was doubtless Sir John Lubbock’s +famous work entitled _Ants, Bees and Wasps_, first published in 1881. +This work was for many years a sort of standard textbook on the +subject, and is still well worth looking into. + +Another book which may be of use is _Animal Intelligence_, by George +Romanes. The sixth edition, which appeared in 1895, devotes more than +one hundred pages to the habits of ants. + +Eric Wasmann has written a great number of books and papers about ants, +one of the best of which has appeared in English as _The Psychology +of Ants and of Higher Animals_, published in 1905. All of Wasmann’s +works are valuable and well worth reading, but they are marred by his +constant references to philosophical and theological matters which are +of no great interest to the general reader. Father Wasmann feels called +upon to demonstrate that ants, as regards their psychical powers, +are much nearer to man than are the anthropoid apes, and is forever +interrupting himself to defend his vitalistic biology and condemn the +theory of organic evolution. + +By all odds the best work available on the subject is the large volume +called _Ants_, written by Professor William Morton Wheeler of Harvard +University, and published in 1910. This book is, in fact, not merely +the best but the only book required by the average student. There is, +of course, a great deal of material which is uncomprehensible to one +who has no particular technical background, but the whole thing is so +admirably arranged that the student has only to glance through the +table of contents to locate matter suited to his taste and training. I +have made a very free use of _Ants_ in the preparation of this booklet, +some sections of which are little more than epitomes or abstracts of +Wheeler’s chapters. + + + + +CHAPTER II + +THE ANT’S BODY + + +The body of the ant, like those of other insects, is segmented, and +covered with a hard chitinous external skeleton. It is separated by +constrictions into three distinct parts, the head, which bears the eyes +and mouth-parts; the thorax, to which the wings and legs are attached; +and the abdomen, which contains most of the entrails and the sexual +apparatus. + +_The Head, Eyes, and Mouth-parts._ The head varies greatly in shape +and size, but always bears a frontal plate or _clypeus_, just above +which the two jointed _antennae_ or feelers are attached. The antennae +contain a great number of minute structures which are supposed to be +connected with the sense of smell. Three small simple eyes or _ocelli_ +are set in the top of the head, and two large _compound eyes_ are +located one on either side. The eyes are always very well developed in +the males, and somewhat less so in the females; the eyes of the workers +are relatively small, and the ocelli are sometimes lacking altogether. +The compound eyes are the principal organs of vision, while the ocelli +are supposed to register only very near objects. + +Just below the clypeus are the mouth-parts, consisting of the _labrum_ +or upper lip, a pair of powerful _mandibles_, another pair of jaws +called _maxillae_, and the _labium_ or lower lip. Both maxillae and +labium bear little _palpi_ or feelers, and are plentifully supplied +with taste-buds containing the gustatory cells. The tongue or _glossa_ +with which the ant laps up its food is attached to the upper part of +the labium. + +_The Thorax, Legs and Wings._ The ant’s thorax consists of four +segments. The first segment is known as the _prothorax_; it is quite +small, and bears the first pair of legs. The next segment, the +_mesothorax_, carries the second pair of legs and the front wings--when +wings are present. The third segment or _metathorax_ bears the +third pair of legs and the hind wings--if there are any wings. The +fourth segment is really a part of the abdomen, and is known as the +_epinotum_. On each side of the thorax are two breathing-holes or +_stigmata_, which communicate directly with the _tracheae_ or windpipes +which supply air to the interior tissues. + +The ant has six legs, one pair attached to each of the three segments +of the thorax proper. Each leg consists of five parts, the _coxa_, the +_trochanter_, the _femur_, the _tibia_, and the _tarsus_ or foot. The +wings are four in number, and the venation is similar to that found +in other members of the order Hymenoptera, but the wings are not much +used in classification because the workers are always wingless, and the +females wear wings only for a part of their lives. + +_The Abdomen and Its Appendages._ The ant’s abdomen is divided into two +parts, the slender _pedicel_ which articulates with the last segment +of the thorax, and the larger part of the abdomen called the _gaster_. +The pedicel is provided with a file-like structure, which by rubbing +against a non-striated segment produces a sound of very high pitch. +In some species the females and workers bear stings and poison glands +in the last segment of the gaster. The female has no ovipositor. In +the male the tip of the gaster usually bears three pairs of sexual +appendages; the two outer pairs are used in clasping the female during +copulation, and the inner pair, when held tightly together, form a +tube which functions as a penis. + +_The Alimentary Canal._ The mouth is located between the maxillae, +and is provided with a little pouch called the _infrabuccal cavity_, +which is used to hold solid matter while the liquid nutriment is +being sucked out of it. When this has been accomplished the pellet +is thrown out. The liquid food passes back into the _pharynx_, and +then on through a slender tube called the _esophagus_, which is lined +with fine hairs. In the gaster the esophagus expands into the _crop_, +which acts as a reservoir; no food is absorbed through its walls, +but is often regurgitated to feed the young. Just back of the crop +is the _proventriculus_ or gizzard, the movements of which provide +the suction by which liquid is drawn up the esophagus and into the +crop, and the force by which food is regurgitated. The true _stomach_ +is rather small, and it is here that the food is both digested and +absorbed. The _small intestine_ communicates with the stomach by a +valve, and is connected with a number of _Malpighian tubes_ which act +as kidneys, absorbing liquid waste from the blood and pouring it into +the intestine. The large intestine or _rectum_ receives the feces and +urine from the small intestine and expels them from the body by way of +the _anal opening_. + +_The Circulatory System._ The _blood_ of the ant, like that of other +insects, is colorless, and contains several kinds of corpuscles. Its +function is to carry food from the stomach where it is absorbed to +other parts of the body where it is needed. The blood of insects has +no red corpuscles, and does not carry oxygen about. The blood is not +confined in definite veins and arteries as in the higher animals, but +percolates about through the entire body cavity. There is a simple +_heart_ in the dorsal part of the abdomen which pulsates and forces +blood forward through an _aorta_ into the head, from which it seeps +gradually back into the abdomen, to be pumped forward through the aorta +again. Thus a sluggish circulation is maintained. + +[Illustration: Fig. I. Diagram showing internal structure. 1, mouth; 2, +pharynx; 3, infrabuccal cavity; 4, aorta; 5, esophagus; 6, heart; 7, +crop; 8, small intestine; 9, stomach; 10, Malpighian tubes; 11, large +intestines or rectum; 12, anal opening.] + +_Respiration._ Ants have neither lungs nor gills, and the blood does +not carry oxygen into the cells and carbon dioxide out as in the higher +animals. As in most other insects, air is taken into the body through +breathing-holes or _stigmata_, and brought into direct contact with the +tissues. There are ten pairs of these stigmata in the ant--two pairs in +the thorax and eight in the abdominal segments. Each opens through a +sort of valve into a _trachea_ or wind-pipe, which branches until its +ramifications extend to all parts of the body. When certain muscles +contract the size of the body increases, and air is drawn in through +the stigmata; when the size of the body is decreased the air is forced +out. The incoming air brings in the necessary oxygen, and the outgoing +current is laden with carbon dioxide waste from the tissues. + +_The Nervous System._ The _brain_ proper is a mass of nerve matter in +the head just above the esophagus, but the _subesophageal ganglion_ is +very close to it, and the two are connected by heavy fibers on each +side of the esophagus, so that the whole thing has the appearance of +a brain with the gullet running through the middle of it. The major +part of the upper brain is connected with the compound eyes, but there +are nerves also which supply the ocelli, the antennae, the pharynx, +the labrum, and muscles in the head. The subesophageal ganglion gives +off nerves to the mandibles, maxillae and labium. From the lower back +part of the subesophageal ganglion the _ventral nerve cord_ arises, and +runs through the thorax and far back into the abdomen. This cord bears +three large _thoracic ganglia_ which innervate the muscles of the wings +and legs. In the abdomen are eleven smaller _abdominal ganglia_, with +nerves running out to supply all of the abdominal organs. The so-called +_sympathetic system_ consists of a few very small ganglia and nerves +not directly connected with the ventral nerve cord, which function in +connection with the digestive organs. + +_The Reproductive Organs._ The _ovaries_ of the female or queen ant +are located in the upper and front part of the gaster, and each is +connected by a slender _oviduct_ with the _uterus_. The uterus is +continuous with the _vagina_, the external opening of which is located +near the tip of the abdomen. At the top of the uterus is a small pouch +called the _seminal receptacle_, which receives the sperm from the male +in copulation. The spermatozoa live in this pouch for several years, +and meet and fertilize the eggs as they descend into the uterus from +the ovaries. + +The organs of the worker are similar to those of the queen, except that +they are very much smaller, and are usually incapable of functioning +normally. Worker ants have never been seen to copulate. The _testes_ +of the male ant are located in the front part of the gaster, and are +connected by the _vas deferens_ with the _seminal vesicles_. Tubes from +the vesicles unite to form the _ejaculatory duct_, which is connected +with the _penis_ at the tip of the abdomen. + + + + +CHAPTER III + +REPRODUCTION AND METAMORPHOSIS + + +Like their relatives the bees and wasps, ants have developed two +types of females, so that a colony contains three distinct sorts of +individuals, known as males, females, and workers. + +_The Male._ The male is less subject to variation than either the queen +or the worker. The body is usually slender and graceful, the eyes and +antennae are well developed, and the mouth parts rather small and weak. +In most species the male is winged. As in the bees, the one great +function of the male in the colony is to copulate with the female or +queen, so as to supply her with sperm to fertilize future eggs. The +male is not killed in the course of the sexual embrace, as the drone +honeybee is, but usually dies soon afterward. + +_The Female._ The true female or queen is usually larger than either +the male or the worker; the head, eyes, and mandibles are well +developed, and the abdomen is very large to contain the reproductive +organs. The female is usually winged at the time of mating, but the +wings are loosely attached and she loses them as soon as the nuptial +flight is over. The wings and legs are stouter and shorter than those +of the male, in most cases. In a few species the females have no wings, +and in others it is the males which are wingless. No case is known in +which neither male nor female is provided with wings. + +_The Worker._ The worker is an undeveloped, wingless female. The eyes +are small, and the ocelli are often lacking; the antennae, legs, and +mouth parts are strong and well developed. There is a great deal +of variation among workers; one common variant is the _dinergate_, +or soldier--a form with a very large head and mandibles adapted to +fighting. The sex organs of the worker are unquestionably female, but +they do not ordinarily function, and a worker has never been seen to +copulate. + +_Mating._ In species in which both the male and female are winged, +mating occurs in the air, as in the nuptial flight of the queen bee. In +the case of the honeybee, however, there is only one queen to a great +number of drones, while with the ants there may be hundreds of queens +and drones in the air, all copulating at once. Another difference is +that the mated females do not often return to the parent colony, as the +queen bee always does. When the mating hour draws near all the ants, +even the nearly blind and wingless workers, rush out of the nest in +great excitement, and the air is soon full of flying ants. Copulation +usually begins high in the air, but the linked pairs often fall to +the ground together. In the mating of bees the male is almost always +instantly killed, the genital organs and entrails being torn out of +his body. This mutilation never happens among ants, but the male’s +life-work is ended with the sexual act, and he usually dies shortly +afterward. + +_The New Colony._ As soon as the mated female is upon solid ground +again she tears off her wings, or removes them by rubbing against +some solid object. This done, condemned to a crawling, terrestrial +existence for the rest of her days, she sets out alone to establish +a new colony. She digs a hole in the ground, or in rotten wood, or +under a flat stone, seals up the opening, and sits down in the dark +until the eggs in her abdomen are mature. Sometimes this takes weeks +or even months, and during this time the queen has nothing to eat, +but lives by absorbing the large wing-muscles which she will never +use again. Finally the eggs are deposited, being fertilized by some +of the spermatozoa which were obtained from the male, and which are +stored in the spermatheca, a little pouch just above the uterus. When +the larvae hatch she feeds them with a secretion from her salivary +glands. The resulting ants are normal workers, except that they are +unusually small. Sometimes it takes nearly a year to rear this first +brood, and all this time the queen has eaten absolutely nothing. As +soon as the workers are old enough they dig passages to the open air, +and enlarge the nest by adding galleries and runways. They drag in +food and feed the exhausted female, who from this time forward does +nothing but eat and lay eggs--the brood being cared for entirely by the +workers. From now on the female is a timid, photophobic, rickety old +egg-laying machine. During her long fast the great wing-muscles have +been absorbed, leaving the thorax hollow, so that she floats if placed +in water. Only a very few females can survive the ordeal necessary to +found a new colony--probably only one of many thousands which undertake +it. It is a beautiful example of the Darwinian phenomena of survival. + +The procedure described above is the usual one in most species of +ants. It was guessed at by Huber in 1810, but the first man to watch +the actual founding of a new colony was an American named Lincecum, +about 1866. In 1879 Sir John Lubbock observed the whole process in an +artificial nest, and his account of the process has since been verified +by numerous other investigators. + +In certain species, however, the queen is unequal to the task of +founding a family in this manner. In this case she must return to the +parent colony, join a queenless colony of her own or an allied species, +or raid a small colony of aliens. In this latter event she kills them +all, and adopts their eggs and brood. + +_Complete Metamorphosis._ Like the butterflies and beetles, ants have +a complete metamorphosis, that is, they pass through four distinct +developmental stages. In many other insects--the grasshoppers for +example--the metamorphosis is said to be incomplete, because the newly +hatched young have the same general form as the adult, and their +development is merely a matter of increase in bulk. + +_The Egg._ Ant’s eggs are very small, rarely more than one-fiftieth of +an inch in length, and are very seldom seen by the casual observer, who +mistakes the comparatively large cocoons for eggs. The egg is usually +elongated, and consists of the germinal spot, the yolk, and the thin +transparent shell called the chorion. The eggs look very much alike, +and one cannot predict whether a given egg will produce a male, a +worker, or a queen. Some eggs are fertilized by sperm stored in the +female’s spermatheca, others are deposited without fertilization, while +those laid by workers are certainly not fertilized, since workers do +not copulate. In bees and certain other related insects it has been +found that unfertilized eggs always produce males, but whether this is +always true in ants is still an open question. + +Very little is known of the embryological development of the ant, but +the unhatched larva certainly has traces not only of antennae and legs, +but remnants of certain abdominal appendages not present in the adult +ant, and evidently harking back to more remote ancestors. The egg +usually hatches about twenty days after it is laid, but the length of +this period varies greatly with the temperature. + +_The Larva._ The newly hatched larva is a soft, semi-transparent grub, +with a fat body, slender crooked neck and small head. There are no +eyes, but the mouth-parts are fairly well developed, and ten pairs of +stigmata are usually present. The body is covered with short fine +hairs. The digestive system is well formed, but there is no connection +between the stomach and the intestine, so that the larva has no +movement of the bowels until it is about to transform into the next +stage. The accumulated feces in the lower part of the stomach may often +be seen as a black spot showing through the semi-transparent walls of +the body. + +[Illustration: Fig. II. Cross-section of an ant-hill, showing the +arrangement of larvae and pupae according to size. (Adapted from +Andre.)] + +The larva is fed by the workers, the food being either regurgitated +liquid food or pieces of fresh vegetable or animal matter. It has been +found in the case of the bees that the kind of food given the larva +determines whether it will develop into a queen or a worker, but we +have no definite information about this matter among the ants. + +When the larva is fully grown, usually about a month after hatching, it +is buried in the ground by the workers, and spins a silken cocoon about +itself. All ant larvae have spinning organs in the head, but some do +not spin cocoons, and in this case are not buried, but undergo their +metamorphosis in the open chambers of the nest. The larva now voids its +accumulated feces, sheds the larval skin, and appears as the pupa, the +third stage in the ant’s development. + +_The Pupa._ In the pupal stage the ant has most of the appendages and +organs of the adult, but they are small and folded close against the +body. The pupa lies quietly, is not fed, and ordinarily gives no signs +of life at all. Gradually the various parts develop, the darker color +of the adult appears, until finally the mature pupa has very much the +appearance of the imago. Then the cocoon is opened by the attendant +workers, the young ant dragged out and fed, and begins its life as an +adult. The pale, newly emerged ant is known as a _callow_. The pupal +stage usually lasts from fifteen to twenty days, but is sometimes much +longer in cold weather. + +_The Adult._ The general appearance and characteristics of the adult +are described elsewhere in this book. The total time of development +from the deposition of the egg to the appearance of the callow varies +from about sixty days to five months, and is considerably longer than +the corresponding period in most other insects. The queen bee, for +example, passes through all three stages in about sixteen days, while +some butterflies are developed in less than twenty-five days. Another +interesting feature is the extreme longevity of the adult ant. The +males are short-lived, but the workers of many species live for four +or five years, and the queens for still longer periods. Janet kept one +for fully ten years, and Sir John Lubbock had a queen in his possession +from December, 1874 to August, 1888, “when she must have been nearly +fifteen years old, and, of course, may have been more,” since he had no +means of knowing her age at the beginning of her captivity. + + + + +CHAPTER IV + +THE HARVESTING ANTS + + +The works of Pliny and other ancient writers contain references to ants +which collected great stores of seeds, and these accounts were quoted +by numerous mediaeval authors. Modern students of ants, however, worked +mostly in northern and central Europe, and as they did not find any of +these harvesting ants they were rather inclined to dismiss the classic +stories as fiction pure and simple, and class the seed-gathering ants +with the unicorn and the mermaid. + +In 1829, however, one W. H. Sykes, an Englishman located in India, +reported that certain ants near his station not only collected great +quantities of grass seed, but after a heavy rain could always be +seen bringing their cereal out of the underground granaries to dry +it in the sun. These observations went far to vindicate the ancient +naturalists, and the work of J. T. Moggridge, in 1873, completed the +vindication. Moggridge watched the workers bring in the seeds, bite +off the germinating part to prevent the seeds from sprouting, and +store them in the nests, which often contain a pint or so of grain. By +examination of these hoards he identified as many as eighteen different +families of plants represented in a single nest. Despite the efforts to +prevent germination by biting off the radicles (a fact noted by Pliny +some sixteen hundred years before) many of the seeds do sprout, and +thus the harvesting ants play a part in the distribution of plants. Of +this subject Moggridge says: “As the ants often travel some distance +from their nest in search of food, they may certainly be said to be, +in a limited sense, agents in the dispersal of seeds, for they not +infrequently drop seeds by the way, which they fail to find again, +and often also among the refuse matter which forms the kitchen hidden +in front of their entrances, a few sound seeds are often present, and +these in many instances grow up and form a little colony of strange +plants. This presence of seedlings foreign to the wild grounds in which +the nest is usually placed, is quite a feature where there are old +established colonies of _Atta barbara_, where young plants of fumitory, +chickweed, cranesbill, Arabis thaleana, etc., may be seen on or near +the rubbish heap.... One can imagine cases in which the ants during +the lapse of long periods of time might pass the seeds of plants from +colony to colony, until after a journey of many stages, the descendants +of the ant-borne seedlings might find themselves transported to places +far removed from the original home of their immediate ancestors.” + +There are many species of harvester ants in America; one of the most +interesting is _Solenopsis geminata_, popularly known as the fire-ant +because of its readiness to use its painful sting. Although the +fire-ant certainly stores up seeds, often to the extent of damaging +crops of soft fruits like strawberries, it will also eat insects, or +almost anything else that it can get. The nests are usually found +beneath flat stones, and in some localities are so common and so +populous that Wheeler refers to the fire-ant as being “in possession +of a large portion of the soil of the American tropics.” In Louisiana +and other southern states these ants nest along the shores of lagoons +and bayous; when the floods come and the nest is submerged the workers +cling together in a ball as much as eight inches in diameter, with the +brood in the center. This ball floats in the water, the ants constantly +shifting about so that very few are drowned, and very little brood +lost, until they are able to effect a landing. + +The so-called Texas harvester (_Pogonomyrmex molefaciens_) has become +famous because a man named Lincecum, about 1862, published a paper in +which he claimed that this ant actually _plants_ seeds in the ground, +weeds and cultivates its fields all summer, gathers the crop, dries +it in the sun, and finally stores it away in subterranian granaries. +This story was accepted and promulgated by Charles Darwin, and so was +believed in many quarters. It seems to rest solely upon the fact that +ant-rice (_Aristida_) is usually found growing about the nest, although +it may occur nowhere else in the immediate vicinity. “Four years of +nearly continuous observation,” writes Wheeler, “enable me to suggest +the probable source of Lincecum’s misconception. If the nests of this +ant can be studied during the cool winter months--and this is the only +time to study them leisurely, as the cold subdues the fiery stings of +their inhabitants--the seeds, which the ants have garnered in many +of their chambers will often be found to have sprouted. Sometimes, in +fact, the chambers are literally stuffed with dense wads of seedling +grasses and other plants. On sunny days the ants may often be seen +removing these seeds when they have sprouted too far to be fit for food +and carrying them to the refuse heap, which is always at the periphery +of the crater or cleared earthen disk. Here the seeds, thus rejected as +inedible, often take root and in the spring form an arc or a complete +circle of growing plants around the nest. Since the _Pogonomyrmex_ +feeds largely, though by no means exclusively, on grass seeds, and +since, moreover, the seeds of Aristida are a very common and favorite +article of food, it is easy to see why this grass should predominate in +the circle. In reality however, only a small percentage of the nests, +and only those situated in grassy localities, present such circles. +Now to state that _molefaciens_, like a provident farmer, sows this +cereal and guards and weeds it for the sake of garnering its grain, is +as absurd as to say that the family cook is planting and maintaining an +orchard when some of the peach stones, which she has carelessly thrown +into the backyard with the other kitchen refuse, chance to grow into +peach trees.” + +Wheeler has also observed the mating flight of the Texas harvester, +and his graphic description is worth setting down in its entirety: +“During three successive years (1901-1903) at Austin, Texas, the +nuptial flight of _molefaciens_ took place on one of the last days +of June (28 and 29) or the first in July. On one of these occasions +(July 4, 1903) the flight was of exceptional magnitude and beauty. A +few days previous the country had been deluged with heavy rains, but +Independence Day was clear and sunny, the mesquite trees were in full +bloom and the air resounded with the hum of insects. For several days +I had seen a few males and winged females stealthily creep out of the +nest entrance as if for an airing, but hurry back at the slightest +alarm. From 1:30 to 3 o’clock, however, on the afternoon of July 4, +all the numerous colonies I could visit during a long walk west of the +town, gave forth their males and females as by a common impulse. The +number issuing from a single large nest was often sufficient to have +filled a half liter measure. Soon every mound and disk was covered with +the bright red females and darker males, intermingled with workers, +many of whom kept on bringing seeds and dead insects into the nest +as unconcernedly as if nothing unusual were happening. The males and +females, quivering with excitement, mounted the stones or pebbles of +the nest or hurriedly climbed onto the surrounding leaves and grass +and rocked to and fro in the breeze. Then, raising themselves on their +feet and spreading their opalescent wings, they mounted obliquely one +by one into the air. I could follow them only for a distance of ten or +twenty meters when their rapidly diminishing bodies melted away against +the brilliant cloudless sky. Many pairs, hesitating to take flight, +chased one another about on the surface of the nest. The amorous males +seized many of the females before they could leave the ground. Lizards +crept forth in great numbers and gulped down quantities of the fat +females, while others were borne off into the air by large robber flies +(_Asilidae_). By a little after three o’clock the males and females had +left the nest and only the workers were seen pursuing the quiet routine +business of bringing in seeds.” + + + + +CHAPTER V + +THE MUSHROOM GROWERS + + +In tropical and subtropical America there are about one hundred species +and varieties of ants which have most extraordinary habits, and are +grouped together in the Myrmicine tribe _Attii_. These ants are usually +rather small and dull colored, and, while they are powerful and +industrious diggers, are not given to rapid movements as most ants are, +but walk slowly and sedately about. When picked up they do not struggle +as many other ants do, but feign death after the manner of certain well +known beetles. + +It was long noted that the _Attii_ carried great quantities of leaves +into their nests, and there was considerable doubt as to the use to +which these were put, some observers believing that they were used +immediately as food, and others contending that they served as roofing +and carpets in the underground passageways. Belt, a naturalist who +lived in Nicaragua, was probably the first to discover the secret +of the leaves. Digging into one of the nests in his garden, he was +surprised to find no great quantity of leaves in any of the passages, +although ants were continually bringing them in at the entrance. The +chambers were always partly filled with “a speckled, brown, flocculent, +spongy-looking mass of a light and loosely connected substance.... This +mass, which I have called the ant-food, proved on examination to be +composed of minutely subdivided pieces of leaves, weathered to a brown +color, and overgrown and lightly connected together by a minute white +fungus that ramified in every direction throughout it.... When a nest +is disturbed and the masses of ant-food spread about, the ants are in +great concern to carry away every morsel of it under shelter again; and +sometimes, when I dug into the nest, I found the next day all the earth +thrown out filled with little pits that the ants had dug into it to get +out the covered up food.” + +Further investigation brought Belt to the conclusion that the _Attii_ +do not eat leaves at all, but use them as manure to grow fungus on; and +further, that they feed upon this fungus, and will eat nothing else. +The _Attii_ are, in Belt’s own phrase, “mushroom growers and eaters.” +While leaves are the chief fertilizer, other substances are often +found suitable for growing fungus on; flowers are sometimes used, and +some species are particularly partial to pieces of orange peel. The +temperature and ventilation of the subterranean gardens are matters +of great importance, and there are many small holes which connect +the larger chambers with the surface. These air-shafts are plugged +and reopened at intervals, and by this means the temperature and +ventilation are regulated. + +Alfred Moeller was a naturalist who studied the _Attii_ in Brazil, and +published the results of his labors in 1893. He found that the gardens +contain only one kind of fungus, all alien spores being carefully +weeded out. The ants do not allow the fruits to develop, and this has +made the classification of the fungi a very difficult matter. The fungi +found in the _Attii_ nests are different from any others known, but +no one can tell whether they are really distinct species or merely +modified forms of certain common moulds or mushrooms. + +Von Ihering, in 1898, discovered that the virgin queen, when leaving +the nest on her nuptial flight, always carries a little pellet of +fungus in her mouth. After being fertilized by the male the queen +shuts herself up in a little burrow and sets about the founding of a +new colony. There are in this case no leaves available, and she starts +the fungus growing upon some of her new-laid eggs, which she crushes +for the purpose, and which seem to work quite as well as the usual +vegetable fertilizer. + +J. Huber, in 1905, studied the same problems which interested Von +Ihering, and concluded that the fungus is not grown upon crushed eggs, +but is nourished by the liquid excrement of the queen. He describes +his observations as follows: “After watching the ant for hours she will +be seen suddenly to tear a little piece of the fungus from the garden +with her mandibles and hold it against the tip of her abdomen, which is +bent forward for this purpose. At the same time she emits from her vent +a clear yellowish or brownish droplet which is at once absorbed by the +tuft of hyphae. Hereupon the tuft is again inserted, amid much feeling +about with the antennae, in the garden, but usually not in the same +spot from which it was taken, and is then patted into place by means +of the fore feet.... According to my observations, this performance +is repeated usually once or twice an hour, and sometimes, to be sure, +even more frequently.” Although, according to Huber, the eggs are not +used directly as fertilizer for the fungus, the same result is brought +about indirectly, as the female is accustomed to feed upon her own +new-laid eggs. Huber estimates that nine out of every ten eggs laid are +eaten at once by the mother. The young larvae, too, are fed with eggs +thrust directly into their mouths by the queen. When the adult workers +appear, however, they live exclusively on the fungus which has been +growing during their larval life, and feed the queen upon fungus also, +while continuing to supply the larvae with their mother’s eggs. After +a week or so the workers dig their way out of the chamber, bring in +leaf-manure for the garden, and the fungus is no longer cared for by +the queen, who now gives all her attention to the serious business of +egg-laying. As the fungus becomes more abundant under this cultivation +it is fed to the larvae also, and eggs are no longer used as food by +any of the individuals in the hive. + +The extraordinary habits of the Attine ants have fascinated many +students, and a number of theories about their development have +been advanced. Forel suggested that the ancestors of the present +mushroom-growers must have lived in rotten wood, and fed upon the +fungus which grew upon the moist walls of their nests, or upon insect +excrement. Von Ihering thinks that they may have developed from the +harvesting ants, which gradually acquired such an appetite for the +fungus which happened to grow in their granaries that the original +stores came to be used only as fertilizer. Wheeler points out that, +besides the Attine ants, there are several kinds of beetles and +termites which cultivate fungus upon their own excrement, and suggests +that originally this was the method employed by the ants. Later on they +came to use the excrement of other insects, and finally passed to the +addition of leaves and other non-fecal vegetable matter. + +As has been said above, the _Attii_ are primarily tropical and +subtropical insects, but a few species have come north into the United +States. They are found chiefly in peninsular Florida, in southern +Texas, and in Arizona, although one species has been reported as far +north as southern New Jersey. + + + + +CHAPTER VI + +THE HONEY ANTS + + +Many species of ants are in the habit of collecting nectar from +flowers, and the sweet juices excreted by plant-lice, until the crop +is greatly swollen. When they arrive at the nest, however, the sweets +are soon regurgitated and fed to the larvae. Any worker ant is able to +expand its crop to a certain extent, but in some species this power is +developed to an enormous degree. In still other tribes this peculiar +capacity seems to be limited to certain individuals. In the true honey +ants only a comparatively small number of workers are capable of this +honey-carrying, and these individuals are known as honey-bearing or +_repletes_. The repletes never accompany the other workers on their +foraging expeditions, but remain always in the nest, and are used as +living bottles in which to store the nectar brought in from the fields. + +In some North American species of _Myrmecocystus_ the abdomen is +distended to such an extent that the repletes are unable to move about +without serious danger of bursting open, and spend their lives hanging +in clusters from the ceilings of certain chambers in the nest. These +honey ants are found in desert regions from central Mexico as far +north as Denver, Colorado, and have since ancient times been highly +prized as sweetmeats by the aborigenes of this region. Honey ants were +described in Mexican publications as long ago as 1832, but the first +important study was made by McCook, whose investigations were carried +out in the so-called Garden of the Gods, near Manitou, Colorado, about +1882. He found several very large nests, covering an area of more than +six feet in diameter, and extending three feet below the surface of +the ground. One of these nests contained some three hundred replete +honey-vessels hanging by their claws from the ceiling, and so distended +with honey that, once fallen from their positions, they were quite +unable to get back up again. McCook saw the ordinary workers bringing +in great quantities of nectar and honeydew, which was immediately +regurgitated and fed to the repletes or _rotunds_, as he called them, +and thus stored up in a living reservoir until needed. + +[Illustration: Fig. III. Repletes of a common honey-ant. (From a +drawing by Wheeler.)] + +It was formerly supposed that the sweet liquid was kept in the stomach +of the replete, but Forel, in 1880, showed that it is in reality +the enormously distended crop which functions. McCook made careful +dissections which bore out Forel’s views, and demonstrated that the +replete has all the abdominal organs of the ordinary worker, although +these are flattened against the body wall and rendered inconspicuous by +the distension of the crop. + +McCook rejected the view that the replete belongs to a separate +caste, saying that “a comparison of the workers with the honey-bearer +shows that there is absolutely no difference between them except in +the distended condition of the abdomen.... The process by which the +rotundity of the honey-bearer has probably been produced, has its +exact counterpart in the ordinary distension of the crop in overfed +ants; the condition of the alimentary canal, in all the castes, is +the same, differing only in degree, and therefore the probability is +very great that _the honey-bearer is simply a worker with an overgrown +abdomen_.... Thus workers are transformed by the gradual distension +of the crop and expansion of the abdomen into honey-bearers, and the +latter do not compose a distinct caste.” + +[Illustration: Fig. IV. Repletes of a honey-ant (_Myrmecocystus +hortideorum_) hanging from the roof of a honey chamber. (After McCook.)] + +Just why these repletes should be developed in some species and not +in others is a mooted question. The fact that they are found only +in desert regions in North America, Australia, and South Africa may +mean that a dry climate is one of the important conditions of the +phenomena. Forel said: “The extraordinary distension of the crop seems +to be frequent in the Australian species of the general Melophorus, +Gamponotus and Leptomyrmex. I suppose that this is due to the extremely +dry climate of the country, which must compel the ants to remain, +often for long periods, in their subterranean abodes. At such times +a store of provisions in living bags must be very useful to them.” +Wheeler, in commenting on the above statement by Forel, writes: “There +can be little doubt of the truth of this statement, but I believe that +it should be expressed in a different manner. The impulse to develop +repletes is probably due to the brief and temporary abundance of liquid +food (honeydew, gall secretions, etc.) in arid regions and the long +period during which not only these substances, but also insect food +are unobtainable. The honey is stored in the living reservoirs for +the purpose of tiding over such periods of scarcity, and the ants +remain in their nests because they do not need to forage. Hence the +confinement mentioned by Forel is not the immediate but one of the +ulterior effects of drought. I am convinced from my observations on +desert ants that no amount of drought will keep these insects in their +nest when they are in need of food. + +“While excavating the nests of _M. hortideorum_ I was impressed with +certain peculiarities in their structure and situation, which seem to +be explainable only as adaptations to the development of repletes. +One of these peculiarities is the great hardness of the soil that is +preferred by the ants. This is the more astonishing because the workers +are very slender and delicate organisms. It is evident that such soil +is well adapted to the construction of vaulted chambers like those in +which the repletes hang, whereas soft or friable soil would be most +unsuitable. The development of repletes also makes it necessary for the +ants to seek very dry situations for their nests. Hence we always find +them, in the environs of Manitou at least, on the summits of ridges +which shed the rain very rapidly. The honey chambers must be kept dry, +both to prevent the disastrous results of crumbling and slipping walls +and to obviate the growth of mould on the repletes, which are, of +course, imprisoned for life in dark cavities and filled with substances +that are favorable to the development of fungi. I believe also that +the size of the nest openings and galleries, which are so much larger +than would seem to be required by such small, slender ants, may be +an adaptation to securing plenty of fresh air in the honey chambers. +If these suppositions are correct, there is obviously a reciprocal +relation between the replete habit and an arid environment: the ants +store honey because they are living in an arid region where moisture +and food are precious, and the storing of honey in replete workers, in +turn, is possible only in very dry soil.” + + + + +CHAPTER VII + +THE LEGIONARY ANTS + + +These insects, which Wheeler describes as “the Huns and Tartars of the +insect world,” are found in tropical Africa and Asia, and in the warmer +parts of America. There is a great variation in size and appearance +between the different castes, the females and workers being blind and +wingless, while the males have well developed wings and large compound +eyes. Some of these ants have no fixed habitation, but wander from +place to place, traveling mostly at night, and camping during the day +in any shallow hole that affords a temporary shelter. They cannot +endure the direct rays of the sun, and Savage, in 1845, observed that +“if they should be detained abroad till late in the morning of a +sunny day by the quantity of their prey, they will construct arches +over their path, of dirt agglutinated by a fluid excreted from the +mouth,” except when they can remain concealed by thick grass or leaves. +Sometimes the soldier ants form a sort of network arch with their own +bodies, and Savage says that “whenever an alarm is given the arch is +instantly broken, and the ants, joining others of the same class on +the outside of the line, who seem to be acting as commanders, guards +and scouts, run about in a furious manner in pursuit of the enemy. +If the alarm should prove without foundation, the victory won or the +danger passed, the arch is quickly renewed, and the main column marches +forward as before in all the order of a military discipline.” + +In these marches the ants carry their eggs, larvae and pupae with them, +these being borne in the mandibles of the _minima_ or small workers, +and the whole column lives by foraging. Savage’s description of their +predatory habits is well worth quoting here: “They will soon kill the +largest animal if confined. They attack lizards, guanas, snakes, etc., +with complete success. We have lost several animals by them--monkeys, +pigs, fowl, etc. The severity of their bite is increased to great +intensity by vast numbers, to a degree impossible to conceive. We may +easily believe that it would prove fatal to any animal in confinement. +They have been known to destroy the _Python natalensis_, our largest +serpent. When gorged with prey it lies motionless for days; then, +monster as it is, it easily becomes their victim.... Their entrance +into a house is soon known by the simultaneous and universal movement +of rats, mice, lizards, Blapsidae, Blattidae, and of the numerous other +vermin that infest our dwellings. Not being agreed, they cannot dwell +together, which modifies in a good measure the severity of the driver’s +habits, and renders their visits sometimes (though very seldom in my +view) desirable. Their ascent into our beds we sometimes prevent by +placing the feet of the bedsteads into a basin of vinegar, or some +other uncongenial fluid; this will generally be successful if the +rooms are ceiled, or the floors overhead tight; otherwise they will +drop down upon us, bringing along with them their noxious prey in the +very act of contending for victory. They move over the house with a +good degree of order, ransacking one point after another, till, either +having found something desirable, they collect upon it, when they may +be destroyed _en masse_ by hot water; or, disappointed, they abandon +the premises as a barren spot, and seek some other more promising +locality for exploration. When they are fairly in we give up the house, +and try to await with patience their pleasure, thankful, indeed, if +permitted to remain within the narrow limits of our beds or chairs. +They are decidedly carnivorous in their propensities. Fresh meat of all +kinds is their favorite food; fresh oils also they love, especially +that of _Elais guiniensis_, either in the fruit or expressed. Under my +observation they pass by milk, sugar and pastry of all kinds, also salt +meat; the latter, when boiled, they have eaten, but not with the zest +of fresh. It is an incorrect statement, often made, that _they devour +everything eatable_ by us in our houses; there are many articles which +form an exception. If a heap of rubbish comes within their route, they +invariably explore it, when larvae and insects of all orders are borne +off in triumph--especially the former.” + +Sometimes, instead of camping in shelters on the ground, these ants +climb up into a tree and hang together in a cluster like a swarm of +bees. Savage reports a colony suspended from a low tree: “From the +lower limbs (four feet high) were festoons or lines of the size of +a man’s thumb, reaching to the plants and ground below, consisting +entirely of these insects; others were ascending and descending upon +them, thus holding free and ready communication with the lower and +upper portions of this dense mass. One of these festoons I saw in the +act of formation; it was a good way advanced when first observed: +ant after ant coming down from above, extending their long limbs and +opening wide their jaws, gradually lengthened out the living chain till +it touched the broad leaf of a _Canna coccinea_ below. It now swung to +and fro in the wind, the terminal ant meanwhile endeavoring to attach +it by his jaws and legs to the leaf; not succeeding, another ant of the +same class (the very largest) was seen to ascend the plant, and, fixing +his hind legs with the apex of the abdomen firmly to the leaf under the +vibrating column, then reaching with his fore-legs and opening wide his +jaws, closed in with his companion above, and thus completed the most +curious ladder in the world.” + +Similar chains are used in bridging little rills or even small brooks, +but when a real flood occurs a different procedure is adopted. In this +case they cling together so as to form a large ball, with the eggs and +young in the center, and float away upon the water until a safe landing +can be effected. + +There are several kinds of legionary and driver ants in America; some +species have been found as far north as Texas and even Colorado, but +most of them are confined to the tropics. These ants usually do not +spend all of their time on the march, but have permanent nests, from +which they sally out at intervals on foraging expeditions. Belt offers +a graphic description of the sortie of a colony in Brazil: “One of the +smaller species (_Eciton praedator_) used occasionally to visit our +house, swarm over floors and walls, searching every cranny, and driving +out the cockroaches and spiders, many of which were caught, pulled or +bitten to pieces, and carried off.... I saw many large armies of this, +or a closely allied species, in the forest. My attention was generally +first called to them by the twittering of some small birds, belonging +to several different species, that followed the ants in the woods. On +approaching to ascertain the cause of the disturbance, a dense body of +the ants, three or four yards wide, and so numerous as to blacken the +ground, would be seen moving rapidly in one direction, examining every +cranny, and underneath every fallen leaf. On the flanks, and in advance +of the main body, smaller columns would be pushed out. These smaller +columns would generally first flush the cockroaches, grasshoppers and +spiders. The pursued insects would rapidly make off, but many, in +their confusion and terror, would bound right into the midst of the +main body of ants.... The greatest catch of the ants was, however, when +they got amongst some fallen brushwood. The cockroaches, spiders and +other insects, instead of running right away, would ascend the fallen +branches and remain there, whilst the host of ants were occupying +all of the ground below. By and by up would come some of the ants, +following every branch, and driving their prey before them to the ends +of the small twigs, when nothing remained for them but to leap, and +they would alight in the very midst of their foes, with the result of +being certainly caught and pulled to pieces. Many of the spiders would +escape by hanging suspended by a thread of silk from the branches, safe +from the foes that swarmed both above and below.” + +[Illustration: Fig. V. Legionary ants attacking a snake.] + +Some of the Brazilian species are more nomadic in their habits. +Belt says: “I think _Eciton hamata_ does not stay more than four or +five days in one place. I have sometimes come across the migratory +columns. They may easily be known by all the common workers moving in +one direction, many of them carrying the larvae and pupae carefully +in their jaws. Here and there one of the light-colored officers +moves backwards and forwards directing the columns. Such a column is +of enormous length, and contains many thousands, if not millions, +of individuals. I have sometimes followed them up for two or three +hundred yards without getting to the end.... They make their temporary +habitation in hollow trees, and sometimes underneath large fallen +trunks that offer suitable hollows. A nest I came across in the latter +situation was open at one side, and the ants were clustered together +in a dense mass, like a great swarm of bees, hanging from the roof +but reaching to the ground below. Their innumerable long legs looked +like brown threads binding together the mass, which must have been at +least a cubic yard in bulk, and contained hundreds of thousands of +individuals, although many columns were outside, some bringing in the +pupae of ants, others the legs and dissected bodies of insects. I was +surprised to see in this living nest tubular passages leading down +into the center of the mass, kept open just as if it had been formed +of inorganic material. Down these holes the ants who were bringing the +booty passed with their prey. I thrust a long stick down to the center +of the cluster and brought out clinging to it many ants holding larvae +and pupae, which were probably kept warm by the crowding together of +the ants. Besides the common dark-colored workers and light-colored +officers, I saw there many still larger individuals with enormous jaws. +These they go about holding wide open in a threatening manner, and I +found, contrary to my expectation, that they could give a severe bite +with them, and that it was difficult to withdraw the jaws from the +skin.” + +Sumichrast, who studied some of the Mexican legionaries in 1863, +noted many seemingly aimless migrations, “which they undertake at +undetermined epochs, but in relation, it appears to me, with the +atmospheric changes. What traveler, passing over the _tierra caliente_, +has not encountered the phalanxes of _tepeguas_ upon the paths of the +primitive forests? What inhabitant of these countries has not, at least +once, been unpleasantly torn from the arms of sleep by the invasion +of his domicile by a black army of _soldados_?... Besides the changes +of domicile which are so generally in relation with the atmospheric +variation as to serve as a rule to the inhabitants of the country, +the _Eciton_ devotes itself every season to excursions for pillage, +destined to supply the larvae with nourishment. Nothing is more +curious than these _battues_ executed by an entire population. Over an +extent of many square meters, the soil literally disappears under the +agglomeration of their little black bodies. No apparent order reigns in +the mass of the army, but behind this many lines or columns of laggards +press on to rejoin it. The insects concealed under the dry leaves and +the trunks of fallen trees fly on all sides before this phalanx of +pitiless hunters, but, blinded by fright, they fall back among their +persecutors and are seized and dispatched in the twinkling of an eye. +Grasshoppers, in spite of the advantage given them by their power of +leaping, hardly escape more easily. As soon as they are taken, the +_Eciton_ tears off the hinder feet and all resistance becomes useless.” + +The same author describes with some feeling their habit of invading +houses. “These visits ordinarily take place at the beginning of the +rainy season, and almost always during the night. The expeditionary +army penetrates the habitation which it proposes to visit at many +points at once, and for this purpose divides itself into many columns +of attack. One is apprised very soon of their arrival by the household +commotion among the parasitic animals. The rats, the spiders, the +cockroaches, abandon their retreats and seek to escape from the attacks +of the ants by flight. Alimentary substances the _soldados_ hold in +no esteem, and they disdain even sugary things, to which the ants in +general are so partial. Dead insects even do not seem to invite their +covetousness. It has often happened to me to be obliged to abandon +my abode, without having time to carry away my collection, to which +they have never done the least injury. The trouble occasioned by these +insects in entering houses is more than compensated by the expeditious +manner in which they purge them of vermin, and in this view their visit +is an actual benefit.” + +As these ants are usually quite blind and their movements are directed +(so far as we can tell) by the sense of smell and contact alone, it +is quite remarkable that they are able to move about so readily, and +become familiar with their surroundings in less time than their seeing +relatives. Forel wrote in 1899: “Throw a handful of _Ecitons_ with +their larvae on a spot with which they are absolutely unacquainted. In +such circumstances other ants scatter about in disorder and require an +hour or more to assemble and bring their brood together and especially +to become acquainted with their environment, but the _Ecitons_ do this +at once. In five minutes they have formed distinct files which no +longer disintegrate. They carry their larvae and pupae, marching in a +straight path, palpating the ground with their antennae and exploring +all the holes and crevices till they find a suitable retreat and enter +it with surprising order and promptitude. The workers follow one +another as if at a word of command, and in a very short time all are in +safety.” + + + + +CHAPTER VIII + +THE RED SLAVE MAKERS + + +The European ant known as _Formica sanguinea_ is blood-red in color, +and is one of the most industrious, versatile, and belligerent insects +known to man. This species, according to Wheeler, “assails any intruder +with its mandibles, simultaneously turning the tip of its gaster +forward and injecting formic acid into the wound.” + +Although _sanguinea_ is widely known as a slave-holding species, it +is by no means wholly dependent upon its slaves, but is quite able +to dig its own nest, gather food and rear young without the aid of +any slaves at all. “There is,” said Wheeler, “nothing to show that +the slaves contribute anything more to the communal activities than +would be contributed by an equal number of small _sanguinea_ workers.” +Many observers have reported slaveless colonies of _sanguinea_ which +seemed to be flourishing, and Wasmann found that the youngest colonies +contain, as a rule, more slaves than the older nests. He also reported +an inverse ratio between the number of slaves and the size of the +colony, some of the very largest being practically slaveless. + +The slave-hunting expeditions of the _sanguinea_ are said to occur +only two or three times a year, and the general procedure is described +by Wheeler as follows: “The army of workers usually starts out in the +morning and returns in the afternoon, but this depends on the distance +of the _sanguinea_ nest from the nest to be plundered. Sometimes the +slavemakers postpone their sorties till three or four o’clock in the +afternoon. On rare occasions they may pillage two different colonies in +succession before going home. The _sanguinea_ army leaves its nest in +a straggling, open phalanx sometimes a few meters broad and often in +several companies or detachments. These move to the nest to be pillaged +over the directest route permitted by the often numerous obstacles in +their path. As the forefront of the army is not headed by one or a few +workers that might serve as guides, but is continually changing, some +dropping back while others move forward to take their places, it is +not easy to understand how the whole body is able to go so directly to +the nest of the slave species, especially when this nest is situated, +as is often the case, at a distance of fifty or a hundred meters. We +must suppose that the colony has acquired a knowledge of the precise +location of the various nests of the slave species within an area of +a hundred meters or more of its own nest. This knowledge is probably +acquired by scouts leaving the nest singly and from time to time for a +period of several weeks, and these scouts must be sufficiently numerous +to determine the movements of the whole worker body when it leaves the +nest. This presupposes not only a high development of memory, but some +form of communication, for the nest attacked is usually one of many +lying in different directions from the _sanguinea_ nest. + +“When the first workers arrive at the nest to be pillaged, they do +not enter at once, but surround it and wait for the other detachments +to arrive. In the meantime the _fusca_ or _rufibarbis_ scent their +approaching foes and either prepare to defend their nest or seize their +young and try to break through the cordon of _sanguinea_ and escape. +They scramble up the grass-blades with their larvae and pupae in their +jaws or make off on the ground. The sanguinary ants, however, intercept +them, snatch away their charges, and begin to pour into the entrance of +the nest. Soon they issue forth one by one with the remaining larvae +and pupae and start for home. They turn and kill the workers of the +slave-species only when these offer hostile resistance. The troop of +cocoon-laden _sanguinea_ straggle back to their nest, while the bereft +ants slowly enter their pillaged formicary and take up the nurture of +the few remaining young or await the appearance of future broods. + +“Forel is of the opinion that many of the young brought home by the +sanguinea are eaten, for the number of those which eventually hatch and +become auxiliaries is very small compared with the number pillaged +during the course of the summer. Wasmann believes, however, that the +forays take place for the specific purpose of obtaining young to rear. +This seems to be disproved by the fact that even small _sanguinea_ +colonies are quite able to get along without slaves and by the +insignificant number of these individuals in many nests. Darwin has +interpreted the surviving and adopted workers as a kind of by-product, +or as representing food which the ants failed to eat at the proper +time, and such they would appear to be in the adult colony, though, as +we shall see, they have an additional significance as the result of an +instinct inherited by the _sanguinea_ workers from their queen. That +the foray is, to some extent at least, due to the promptings of hunger, +seems to be shown by the fact that _sanguinea_ sometimes plunders the +nests of ants which it could not adopt as slaves.” + +Wasmann describes the military expeditions of the so-called sanguine +slavemakers (_F. sanguinea_), which generally hunt in companies of +from twenty to fifty workers, “with the purpose not only of stealing +the neuter pupae of the slave species, but often also of pillaging +the nests of smaller ants belonging to the genus _Lasius_, the +larvae, pupae and winged individuals of which are carried off to be +devoured. During the time of the nuptial flight of _Lasius niger_, many +_sanguinea_ colonies are hunting in the vicinity of their nest for the +heavy _Lasius_ females which drop to the ground. Then either singly +or with united forces these robbers pull their victims into their +strongholds, where they are mercilessly slaughtered. On the afternoon +of August 24, 1888, I witnessed such a typical hunting expedition of +several _sanguinea_ colonies near Exaten, Holland, on the outskirts of +a fir plantation. The road passing the nests was covered far and wide +with _sanguineas_ rushing upon every _Lasius_ female that dropped from +the air, as upon a welcome booty. Within the space of an hour I counted +more than one hundred females of _Lasius niger_ that fell victims to +the hunters.” + +There are several species and sub-species of _sanguinea_ in the United +States, and the habits of these differ in several particulars from +those of their European relatives. Wheeler reports that although he +has found plenty of slaveless colonies, most nests contain slaves in +much greater number than do similar colonies in Europe. He thinks this +due in part to the fact that the American species make more frequent +raids, and partly also because the species chosen as slaves are “much +more cowardly and docile” than the victims of the slave-hunters of +the Old World. The actual tactics employed in the raids do not differ +essentially from those of the European species. + +It was long supposed that new colonies of the _sanguinea_ were founded +in this wise: When the queen descends from her nuptial flight she +either brings up a brood of her own like many common ants, or she is +adopted into a nest of one of the slave species. On either of these +suppositions it is difficult to explain how the slave-making instincts +could be transmitted to the workers, because the latter have no +offspring and the queen was supposed to lack the slaving instincts. In +1906, Wheeler cleared the matter up by introducing a _sanguinea_ queen +into a nest containing workers, larvae, and cocoons of one of the slave +species. She was immediately attacked, but beat off her assailants, +killed a number of them, and captured a large number of cocoons, which +she carried into a separate chamber and defended against all comers. +Here she waited until the workers emerged from the captured cocoons; +these workers, of course, attached themselves to her and soon gained +possession of the whole nest. This experiment shows clearly that the +_sanguinea_ queen really possesses all the slave-making tendencies +exhibited by the workers in their raiding, and solves the problem of +the inheritance of these instincts. + + + + +CHAPTER IX + +THE AMAZONS AND THEIR SLAVES + + +Another type of slave-owning ants is represented by the genus +_Polyergus_, found in both Europe and North America, and known as +amazons. Slavery among the amazons is a very different thing from +the casual master-servant relationship found in the various species +of sanguinary ants. The _sanguinea_ are quite able to build nests, +gather food, and rear their young unaided by slave labor, and slaveless +colonies are not at all uncommon, but the amazons are absolutely +dependent upon their slaves, and no amazon colony could exist without +them. As Wheeler says, the amazons “are even incapable of obtaining +their own food, although they may lap up water or liquid food when +this happens to come in contact with their short tongues. For the +essentials of food, lodging and education they are wholly dependent on +the slaves hatched from worker cocoons that they have pillaged from +alien colonies. Apart from these slaves they are quite unable to live, +and hence are always found in mixed colonies inhabiting nests whose +architecture throughout is that of the slave species. Thus the amazons +display two contrasting sets of instincts. While in the home they sit +about in stolid idleness or pass the long hours begging the slaves for +food or cleaning themselves and burnishing their ruddy armor, but when +outside the nest on one of their predatory expeditions they display +a dazzling courage and capacity for concerted action compared with +which the raids of _sanguinea_ resemble the clumsy efforts of a lot of +untrained militia. The amazons may, therefore, be said to represent +a more specialized and perfected stage of _dulosis_ than that of the +sanguinary ants. In attaining to this stage, however, they have become +irrevocably dependent and parasitic.” + +The same author describes a slave-hunting foray of the European +species. “The ants leave the nest very suddenly and assemble about +the entrance if they are not, as sometimes happens, pulled back and +restrained by their slaves. Then they move out in a compact column +with feverish haste, sometimes, according to Forel, at the rate of a +meter in 33 seconds, or 3 cm. per second. On reaching the nest to be +pillaged, they do not hesitate like _sanguinea_ but pour into it at +once in a body, seize the brood, rush out again and make for home. +When attacked by the slave species they pierce the heads or thoraces of +their opponents and often kill them in considerable numbers. The return +to the nest with the booty is usually made more leisurely and in less +serried ranks. The observer of one of these forays cannot fail to be +impressed with the marvelous precision of its execution. Although the +ants may occasionally lose their way and have to retrace their steps or +start off in a different direction, they usually make straight for the +nest to be plundered. They must, therefore, like _sanguinea_, possess a +keen sense and memory of locality. There can be little doubt that they +often leave the nest singly and make a careful reconnoissance of the +slave colonies in the vicinity.” + +One can hardly believe that as soon as the fighting is over these +warriors relapse into their accustomed lethargy, and are fed and cared +for by their slaves, who often prevent them from leaving the nest, +and sometimes, when they have wandered away, pick them up bodily and +carry them home by main strength. When a colony moves to a new home +the whole enterprise is left to the slaves, who choose and prepare the +new nesting site, and carry the warriors to it. In the case of the +_sanguinea_ it will be remembered that it is the masters who carry the +slaves on these occasions. + +An American amazon which has been the subject of considerable study is +_Polyergus breviceps_, found in the mountainous regions of Colorado +and New Mexico. This species is very striking in appearance, the +worker and queen being of a rich purplish-red color, while the male +is jet-black with white wings. A peculiar feature of the _breviceps’_ +raiding parties is that there are no casualties on either side. The +slave species offer no real resistance, and the amazons simply put them +gently to one side, take their larvae and pupae, and go their way. + +We do not know exactly how new amazon colonies are established. Forel, +Wasmann and Viehmeyer have agreed that the queen lacks the domestic +instinct, and therefore the new colony must be founded by the slave +species, which cares for the amazon females. It has been shown that the +adoption occurs readily enough in artificial nests. Some experiments by +Wheeler gave rather conflicting results, and he closes his discussion +of the matter by saying: “It will be necessary, therefore, to study +this question further before making definite statements in regard to +the method employed by our American amazons in establishing colonies.” + + + + +CHAPTER X + +DAIRIES AND GUESTS + + +The peculiar symbiotic relations between ants and aphids is worth a +brief description. The aphids or plant-lice live in colonies upon +certain plants, and feed upon juices which they suck from the foliage. +The liquid excrement of these insects is sweet, and a surprisingly +large amount is voided--Bŭsgen found that the maple aphid produces +as many as forty-eight drops in twenty-four hours. This substance is +sometimes so abundant that it covers the leaves and even drips down to +the ground; it is known as honeydew, and some rustics still believe +that it somehow falls from heaven. The ants are very fond of this +honeydew, and some species live upon it almost exclusively at certain +seasons, and locate their nests always near good aphid-pastures. The +ants never kill and eat aphids as they do other insects, but protect +them against their enemies. They even carry them about from one pasture +to another, and some species build little sheds and corrals in which +their aphids are confined just as we confine cattle. Sometimes the ants +simply lap up the honeydew as it falls upon the leaves, but in most +cases they _milk_ the aphids by gently stroking them with the antennae, +which causes the emission of a drop of the sweet liquid. Some kinds of +aphids have developed a circle of stiff hairs around the anal opening, +which thus retains the honeydew till the ant comes for it. Not only do +the ants care for and milk the adult aphids, but they rear them from +the eggs. Huber, Lubbock and others have seen ants collecting aphid +eggs in the Autumn, and it has been found that these eggs are stored in +the nest until they hatch, when the young plant-lice are carried out +and placed on a suitable food-plant. On cold or rainy days they are +taken back into the nest; when the weather moderates the ants carry +them out to pasture again. + +The scale-insects and mealy-bugs (_Coccidae_) also produce honeydew, +and are visited by the ants precisely as the aphids are. The _manna_ +of the Biblical story, according to Wheeler, “is now known to be the +honeydew of one of these insects (_Gossyparia mannifera_) which lives +on the tamarisk. This excretion is still called _man_ by the Arabs who +use it as food.” Forel, Cockerell and Wheeler have seen ants tending +great herds of coccids, and a few of these insects are found in many +nests. + +Several kinds of tree-hoppers bear a similar relation to ants. Bare, +who studied these matters in Argentina, “watched the larvae of various +species of _Centrotus_ being assiduously attended by ants. The larvae +are gregarious, frequenting the succulent shoots of plants, and have an +extensile organ at the extremity of the body, from which the coveted +fluid is emitted.” Wheeler observed whole colonies of ants herding +leaf-hoppers in Colorado, and reports that these novel milk-cows +“responded to the antennal caresses of the ants in precisely the same +manner as the plant-lice and scale-insects.” Some ants confine their +tree-hoppers in sheds and shelters similar to those used for the aphids. + +The relationship of ants to certain small caterpillars (the larvae +of some of the _Lycaenid_ butterflies) has been known for a long +time. These little caterpillars, when caressed on the posterior +end by the antennae of the ants, give up a drop of sweet liquid, +doubtless very similar to that produced by the aphids and coccids. +These larvae are often found in the ants’ nests, and some of the newly +emerged butterflies have been seen to come out of the ant-hills. +It is said that the ants protect the caterpillars from the attacks +of hymenopterous parasites, and De Niceville is authority for the +statement that the butterfly will not lay her eggs when there are no +ants about: “If the right plant has no ants, or the ants on that plant +are not the right species, the butterfly will lay no eggs on that +plant. Some larvae will certainly not live without the ants, and many +larvae are extremely uncomfortable when brought up away from their +hosts or masters.” + +[Illustration: Fig. VI. A small myrmecophilous cricket (_Myrmecophila +nebrascensis_) gnawing at the tibia of the Texan harvester-ant. (After +Wheeler.)] + +Besides the ants’ relationship with the insects which produce sweet +substances, there are symbiotic relations of a very different type with +a group of insects known as _myrmecophiles_--ant-guests. These insects, +at one stage or another, live in the ant-hills. At least fifteen +hundred species of ant-guests are known, and Escherich estimates that +there must be at least three thousand altogether. Wheeler thinks that +even this estimate is probably too low. At least a thousand of the +known species are beetles, and most of the rest are insects of one kind +or another, but there are about sixty arachnids and a few crustaceans. + +Some of the myrmecophiles are not _friends of ants_ as the name +implies, but mere interlopers--scavengers, robbers and assassins. +There are a number of small beetles which live in the less frequented +galleries of the nest, eat dead ants and brood, kill ailing or crippled +ants, and even attack healthy adults when they catch them alone or +at some disadvantage. Some of these beetles resemble ants in general +appearance, a mimicry which is doubtless of considerable value to +them. The ants kill these pests whenever they can, but many are +protected by their ability to emit an evil-smelling substance which +puts the ants to flight. Others will be killed at once if confined in a +small chamber with a few ants, but in a large nest are able to escape +by reason of their agility. + +Another class of myrmecophiles, known as _synoeketes_, or tolerated +guests, live in the ant-hills without attracting any great attention, +being treated with contemptuous indifference by their hosts. The larvae +of certain moths and flies, a large number of beetles, and numerous +other insects are of this class, and feed largely upon the refuse of +the kitchen-middens. Wasmann has studied a group of beetles which +live with the nomadic Doryline ants. These camp-followers mimic the +legionaries, and march along in their columns apparently unnoticed, +being allowed to share the prey taken by the blind warriors. Other +beetles live in the nests of the _sanguinea_, and feed largely upon the +tiny parasites from the bodies of their hosts. Certain minute wingless +crickets are very abundant in many nests; they are seen to lick the +bodies of the ants, and it is supposed that they live upon some +cutaneous secretion. + +The insect called _Attaphila_ is a sort of miniature cockroach, which +lives with the fungus growing _Attii_, and is, according to Wheeler, +the only insect known to be on intimate terms with these ants. A +peculiar thing about the _Attaphila_ is that the last joint of the +antennae is nearly always bitten off. This insect was formerly +supposed to feed on fungus, but has since been found to lick the +surface secretions from the ants’ bodies. A little beetle called +_Oxysoma oberthueri_ is very like _Attaphila_ in its habits, “mounting +the bodies of its host and licking or shampooing them with great +eagerness.” + +Very different from the furtive, barely tolerated myrmecophiles +described above are the three or four hundred species known as true +guests, which, to quote Wheeler again, “are no longer content to be +treated with animosity or indifference, but have acquired more intimate +and even friendly relations with the ants. These true guests are not, +therefore, to be found skulking in the unfrequented galleries of the +nest, or suspiciously dodging about among the ants, but live in their +very midst with an air of calm assurance, if not of proprietorship.” +Among these are many beetles bearing tufts of hair which produce some +aromatic secretion very pleasing to the ants. The ants rush to lick the +odorous tufts, are caressed by the peculiar antennae of the beetle, +and feed the latter with regurgitated food. Many of these beetles are +cleaned and shampooed by the ants, are often carried about, and favored +in other ways, despite the fact that they sometimes devour the ant +brood. Some of the smaller species are totally blind, and are permitted +to ride about on the ants’ backs for hours at a time. + +Another sort of guest is the little mite called _Antennophorus_, +which Janet has found in the nests of several European ants. These +mites attach themselves firmly to the body of their host, and it is +interesting to note that no matter how many are present on a single +ant, they are always so placed that the weight is properly distributed, +and the host’s progress not interfered with. These creatures remind +one of the ticks found on higher animals like dogs, but they are not +parasites in the sense that ticks are--they do not suck the ant’s +blood, but reach out and snatch their nutriment from the drops of +regurgitated food as they pass from one ant to another. + +[Illustration: Fig. VII. Showing two minute myrmecophilous beetles +(_Oxysoma oberthueri_) feeding on the surface secretions of an ant. +(Adapted from Escherich).] + +The ants do not bother _Antennophorus_ much, but there is another mite +called _Cillibano_ which is a true blood-sucker, and which they seize +and tear to pieces whenever they can. A little blue fly (_Orasema +viridis_) is common in the nests of several Texan and Mexican ants; its +larvae attach themselves to the ant larvae and live as parasites. Both +the larvae and the adult, however, are fed and fondled by the ants. + +Besides these external parasites there are many grubs and worms which +live inside the body of the ant, and are comparable to the pin-worms +and tapeworms which dwell in the human intestine. These creatures have +not been studied extensively, however, and very little is known of +their habits and metamorphosis. + + * * * * * + + + + +Transcriber’s note + + +Minor punctuation errors have been changed without notice. Italization +was standardized. + +Illustrations tags have been moved so they do not break up the +paragraphs. + +Spelling was retained as in the original except for the following +changes: + + Page 7: “female during copulalation” “female during copulation” + Page 17: “the arangement of larvae” “the arrangement of larvae” + Page 18: “the ant’s tevelopment” “the ant’s development” + Page 29: “habits of the Attiine” “habits of the Attine” + Page 29: “besides the Attiien ants” “besides the Attine ants” + Page 44: “itself every reason to” “itself every season to” + Page 50: “of several _sanquinea_” “of several _sanguinea_” + Page 51: “the _sanquinea_ queen” “the _sanguinea_ queen” + Page 55: “is known as honey dew” “is known as honeydew” + Page 55: “honey dew, and some species” “honeydew, and some species” + + +*** END OF THE PROJECT GUTENBERG EBOOK 77638 *** |