INTRODUCTION.

My design in this Introduction, is to take a rapid review of the facts collected by several writers relative to the History of Ants. The descriptive part, better known than that which refers to their manners and habits, still presents some doubts which I shall attempt to remove. De Geer, among the ancient, Fabricius and Latreille among the modern naturalists, are those to whom I shall have recourse for their classification.

Systematic authors have placed Ants in the class of insects with four naked wings—with Bees, Wasps, Andrenæ, &c. from which they differ essentially in the composition of their families, where we find the males and females furnished with wings, and the workers without them.

The characters given by M. Latreille, to distinguish them more particularly, are that of having “the peduncle of the abdomen surmounted with a scale, or knotty; the abdomen of the workers and females ejaculating an acid, or armed with a sting; the antennæ filiform, or slightly enlarged at their extremity, bent or fractured in the middle, composed of twelve or thirteen joints; the second conical, of the same length as those that follow; a tongue, spoon-shaped, entire; the upper lip effaced; the palpi filiform unequal, anterior of five, posterior of four joints. The first of these characters furnishes two very distinct families, the one, composed of all those ants that have the peduncle surmounted by a scale, the other, of all those in which it is formed of two knots. The characters of the first family, are—having the antennæ filiform, or pointed at the extremity; no sting; a simple venom-bag; the abdomen more elongated, and composed in the females and workers of five rings.”

The ants of the second family have the antennæ moniliform, and considerably enlarged at their extremity; a sting; the abdomen short, and composed of four rings in females and the workers.

The males have, in general, the antennæ longer, and of thirteen joints; the abdomen is composed of one ring more than in other individuals of their species; they possess neither a sting nor a venom-bag. As we shall treat in this work of none but indigenous ants, all of which find place in this general division, I shall not enter into greater detail relative to their classification.

Let us examine separately all the parts of the body of ants in order to know their external organs. Their head is triangular, oblong, and terminates in a point more or less obtuse; it is thick at the top, thin at the opposite extremity, and terminated by two large teeth, termed mandibles; underneath is the mouth, properly so called. On each side are large reticulated oval eyes; above, we commonly notice three more, very small, and placed so as to form a triangle. In the fore-part of the head are the antennæ, and underneath the lower jaws the palpi.

The mandibles of the females and the workers are of a horny structure, concave, curved, denticulated, moveable, and serve for several purposes: those of the males are very slender, terminate in a point, and are covered with hair. Besides these organs with which the mouth is externally furnished, we also remark an upper lip, slightly projecting, two inferior jaws, very small, which play from right to left, and a lower lip, hidden entirely underneath; we are not yet agreed as to their composition.

Fabricius gives to Ants of all kinds, for their principal character, that of having a mouth destitute of a tongue (os absque Lingua); Latreille, on the contrary, grants them one, expressing it under this form (Langue en cuilleron entière); “the lower lip,” he says, “is formed of a conical furrow, coriaceous, with an elevated ridge in the middle, and terminated in a point, and of a tongue, or membranous portion, lodged in this furrow, and spoon-shaped.”—I beg leave to add some few observations to those of these great naturalists. When the ants wish to drink, we see proceed from their lower jaws, which are much shorter than the upper, a little conical, fleshy, and yellowish tubercle, which performs the office of a tongue, advancing and retiring alternately; it appears to proceed from what we term the lower lip, which serves as the base, and perhaps a sheath to this tongue, and which is so small, that it is only from analogy with other insects we have given it this name. This lip is capable of advancing conjointly with the two lower jaws, and when the insect wishes to lap, the whole apparatus makes a progressive movement, in such a way, that the tongue, which is very short, has no need of much extension to enable it to accomplish its object. The jaws are elongated, enlarged at their extremity, slightly concave underneath, of a horny substance, and, compared to the mandibles, extremely slender and weak. In the centre, externally, we notice palpi of six rings each, and two more may be also perceived at the base of the tongue; the latter are much smaller and composed only of four rings: we are as yet unacquainted with their use.

The antennæ, as we have before stated, are bent or fractured, situated in the fore-part of the head, more or less near the middle of the forehead; they lie in a small longitudinal furrow, and are composed of twelve or thirteen joints; the first being about half their length. The antennæ of those ants that have a scale upon the fillet of the abdomen are filiform, and are composed of rings of the same size, or terminate slightly in a point. The ants of the second family have the antennæ, on the contrary, enlarged at the extremity; those of the males are setaceous in the first species, more granulated in the latter species, and in all are formed of one ring more than in the workers and females.

The head is connected to the thorax or corslet by a thin, short, and narrow neck, of a fleshy substance, and furnished with muscles, by which all its movements are regulated.

The corslet of the winged individuals is very large comparatively to the head; that of the workers is much narrower; that of the former is convex, entire, composed of several horny pieces, of different forms, retained by proper membranes: the superior is separated from the sternal portion by a furrow, in the middle of which the wings are implanted. The wings are placed in the back part of the corslet, whilst, in other insects of the same kind, they are situated more in front of the body. Another remarkable character respecting their insertion is,—that the corslet has none of those instruments (Cuillerons) destined to moderate the movements of the wings, and which are situated at their base in the other hymenopterous insects.⁠[1]⁠

The corslet of the workers is gibbous, divided equally, and composed, according to De Geer, of three pieces; the first—that nearest the head, is thick and round; the second is of less size, extends to the under part of the abdomen, and appears divided in two transversely; the third, much thicker than the second, is truncated and obtuse. We cannot well define the form of the corslet, since it varies according to the species; it has four stigmæ, two of which rest in a slight lateral depression (which seems to divide the corslet), one on each side; the other two are situated near the posterior extremity, to the right and left of the fillet.

The wings, which are four in number, are transparent, large, and sleek; the posterior are shorter than the anterior, their nervures are slightly coloured, and the stigma is yellow or brown. These wings are hooked when the insect flies; they form but one horizontal surface by means of a series of little hooks disposed at their margin.

To each of the three lower parts of the corslet are attached a pair of legs. They are connected by a moveable piece, long and conical, which we may term the hip. The posterior legs are the longest; they are each divided into three principal parts—the thigh, the leg, and the foot or tarsus; the latter is formed of five conical pieces, of unequal length, articulated together, and more or less hairy; the tarsus is terminated by two hooks, between which lies a round substance, which we may regard as the sole of the foot. We remark, at the extremity of the leg, properly so called, a spine or spur, straight, strong, and smooth; that on the anterior feet is slightly curved, and covered with stiff hair, where it is connected to the foot. The first piece of the tarsus, which is opposite the spur, presents a considerable curvature. It is furnished with a fringe-work of strong hair, cut regularly. This constitutes the brush which the insect employs when cleaning its antennæ, head, and corslet; it has also other uses, but to these I shall allude on another occasion.

The vertical scale is heart-shaped, with the point turned downwards. It is traversed at its origin by the abdominal fillet; its form varies, and it furnishes very distinct characters. Latreille remarks that it is provided with two stigmæ, which are situated at its base on the posterior side.

The abdomen or belly of the ant is always larger than the corslet, of an oval form, swoln, and more or less pointed at the posterior extremity. It is composed of demi-rings, which are of a horny substance; the superior are connected with the inferior by means of a flexible membrane, which allows of their separation and approximation at will. It is easy to notice this when the insect has taken a full meal, since each of these horny pieces appears then to be separated from the rest by a little whitish band, which is nothing more than this membrane. The abdomen is composed of four or five rings, the last of which gives passage to the sexual organs and the sting.

Latreille regards the scale as characteristic, which rests on the fillet of the abdomen, and takes the place of a ring, which, without that, would be wanting in the abdomen of these insects. These are his words:—“Naturalists,” he says, “have not considered that this scale or these knots on the peduncle of the abdomen of ants are only the first rings shaped in this way. Several wasps have also the first segment of the abdomen formed like a knot. To decide this point, let us count the number of rings of which the abdomen of ants is composed; we know, and it is a constant rule with respect to insects of this order, that there are seven rings in the abdomen of males, and six in that of females. Let us see if, after taking away the scale and the knots of the peduncle, we shall find this number. We do not:—for the abdomen of the females or workers, which has a scale or single knot in the fore-part, possess but five rings, and that of the males only six. The abdomen of those ants whose peduncle is formed of two knots, will have still one ring less; that is to say, four in some, and five in others.”—We have already remarked, that the workers and females of some species are provided with a sting; this consists of a little short, horny substance, straight and conical, formed of two filaments, and accompanied with two other little pieces, conical, smooth, compressed, one on each side. “There exists,” continues M. Latreille, “the greatest resemblance between the exterior organs of generation in single females and workers; the resemblance indeed is so close, that on the most severe examination we can scarcely perceive any sensible difference.” He regards the workers as impotent females, whose organs have not received their full development. In truth, if we consider the form of their head and their teeth, the number of the joints or articulations in their antennæ, the number of their rings, the presence of the sting, or that of the venom-bag which replaces it, we shall be struck with the similarity existing between these two orders. The workers are much smaller than the females; they also differ in the form of the corslet, in the absence of wings, and in colour. Some of the males are smaller, others larger than the workers of their species; their corslet is shaped like that of the females; the scale or knots are of great similarity in all the individuals of each family: the males are commonly of a blackish hue.

Our knowledge of the manners and habits of ants is extremely limited, consisting only of a small assemblage of detached facts, and of a few assertions, sufficiently vague, which I shall discuss in their proper place. In the list of modern authors who have contributed to the history of ants, we find naturalists of the greatest celebrity.

Leeuwenhoeck is the first who seriously attended to the metamorphoses of ants, and proved that what had been hitherto regarded as their eggs were the real larvæ; indeed from their magnitude this should have been previously known, the eggs of these insects being exceedingly minute.

Swammerdam confirms, by profound researches and admirable descriptions, the observations published by his predecessor:—he notices the several changes ants undergo, and shows the pupa to be the same individual that under the form of larva possessed neither limbs nor any distinct features. He points out the distinction between the males and females, which, he says, are furnished with wings, and remarks, that the common ants are labourers or neuters, as obtains in bees. He also describes some of the domestic occupations in which ants are engaged, and informs us, that the larvæ of some species spin a silken envelope, in which they undergo their transformation, and then gives us excellent descriptions of several species of ants.

Linnæus comes next:—he describes seven species of ants met with in Sweden;—treats of the large conical ant-hills abounding in fir-forests; finds the female ants, as well as the males, furnished with wings; which, he says, they lose a little time after birth, and is of opinion they never return to their original habitation.

Geoffroy adds nothing to the facts brought forward by these excellent naturalists: he falls, on the contrary, into several errors, which, as they have been combated by De Geer, I shall pass over in silence.

This last author (De Geer) informs us, that the young ants cannot extricate themselves from their silken envelope without the assistance of the labourers; and that the larvæ of the shining black ant do not always spin, since we find in their nest pupæ both naked and enclosed. He also observes that the larvæ of certain species pass the winter in that state, and that those of the Yellow Ant are closely invested with hair in the month of April, &c.—Passing from the infant to the adult state of the ant, he notices their amours in the air, believes that the females return to their nest to deposit their eggs, in this respect opposing the opinion of Linnæus, who was, however, better informed on this subject than himself. This justly celebrated naturalist, notwithstanding, gives us more information upon the history of ants than the whole of his predecessors.

Charles Bonnet was in his turn occupied:—he was of opinion that ants are directed in their migrations by the scent. He notices a small family-establishment of these insects on the head of a thistle, of which he gives us an interesting account. Had he, however, opened it, he would have, with admiration, discovered the motive which drew them thither, and would no longer have been astonished at their living there without touching the provision he tendered them. He saw these ants engaged in carrying each other, and describes their proceedings in his usual lively and agreeable manner, although unaware of the purport for which these insects had assembled.

M. Latreille confirms the facts brought forward by other authors. He notices two species of ants destitute of eyes, but does not describe their manners. He also advances some conjectures to which we shall refer hereafter.

It appears from all the observations made to the present day, that we are not agreed as to the fate of the males and females; that we know not why certain larvæ should, others should not, spin; why among some species we should find pupæ both naked and enclosed; that we have not sufficiently attended to the spirit which reigns in the interior of ant-hills, nor to the relation existing between the labouring ants and their females; that we have not discovered whether they possess the means of understanding each other; that we have not sufficiently described the construction of their abode, nor the manner in which they establish it, nor do we know whether these insects do or do not form colonies, &c. The number of questions not yet solved is endless; it is, however, time to fill up some of the numerous sketches which our predecessors have left us upon this subject, and place, if possible, the history of ants on a more solid and secure foundation.