NT anatomy becomes a very interesting study when we note the vigorous way the ant uses it—even to the least part. The slender waist characterizes the ant as well as the wasp; the three regions of the body are easily seen, the head with its ever moving antennæ, the slender thorax with its three pairs of most efficient legs, and the long abdomen. The ant's legs are fairly long as compared with the size of the body and the ant can run with a rapidity that, comparatively, would soon outdistance any Marathon runner, however famed. I timed an ant one day when she was taking a constitutional on my foot rule. She was in no hurry, and yet she made time that if translated into human terms would mean 16 yards per second. In addition to running, many ants when frightened will make leaps with incredible swiftness.
A common ant.
The ant does not show her cleverness in her physiognomy, probably because her eyes seem small and dull and she has a decidedly "retreating forehead;" but the brain behind this unpromising appearance is far more active and efficient than that behind the gorgeous great eyes of the dragon-fly or behind the "high brow" of the grasshopper. The ant's jaws are very large compared with her head; they work sidewise like a pair of shears and are armed with triangular teeth along the biting edges; these are not teeth in a vertebrate sense, but are like the teeth of a saw. These jaws are the ant's chief utensils and weapons; with them she seizes the burdens of food which she carries home; with them she gently lifts her infant charges; with them she crushes and breaks up hard food; with them she carries out soil from her tunnel, and with them she fights her enemies. She also has a pair of long palpi, or feelers.
The antenna-comb on the front leg of an ant.
Although her eyes are so small and furnished with coarse facets, as compared with other insects, this fact need not count against her, for she has little need of eyes. Her home life is passed in dark burrows where her antennæ give her information of her surroundings. Note how these antennæ are always moving, seeming to be atremble in eagerness to receive sensations. But aside from their powers of telling things by the touch, wherein they are more delicate than the fingers of the blind, they have other sense organs which are comparable to our sense of smell. Miss Fielde has shown that the five end segments of the antennæ have each its own powers in detecting odor. The end segment detects the odor of the ant's own nest and enables her to distinguish this from other nests. The next, or eleventh segment, detects the odor of any descendant of the same queen; by this, she recognizes her sisters wherever she finds them. Through the next, or tenth segment, she recognizes the odor of her own feet on the trail, and thus can retrace her own steps. The eighth and ninth segments convey to her the intelligence and means of caring for the young. If an ant is deprived of these five end-joints of the antennæ, she loses all power as a social ant and becomes completely disenfranchised. Miss Fielde gives her most interesting experiments in detail in the Proceedings of the Academy of Natural Sciences of Philadelphia, July and October, 1901.
Ants making their toilets.
It is natural enough that the ant, depending so much on her antennæ for impressions and stimuli, should be very particular to keep them clean and in good order. She is well equipped to do this, for she has a most efficient antennæ brush on her wrist; it is practically a circular comb, which just fits over the antenna; and to see the ants using these brushes is one of the most common sights in the ant-nest and one of the most amusing. The ant usually commences by lifting her leg over one antenna and deftly passing it through the brush, and then licks the brush clean by passing it through her mouth, as a cat washes her face; then she cleans the other in a similar manner and possibly finishes by doing both alternately, winding up with a flourish, like a European gentleman curling his mustaches. Her antennæ cleaned, she starts promptly to do something, for she is a little six-footed Martha, always weighed down or buoyed up by many duties and cares. Keeping her antennæ on the qui vive, she assures herself, by touch, of the nature of any obstacle in her path. If she meets another ant, their antennæ cross and pat each other, and thus they learn whether they are sisters or aliens; if they are sisters, they may stand for some time with their antennæ fluttering. One who has watched ants carefully, is compelled to believe that they thus convey intelligence of some sort, one to the other. The ant is a good sister "according to her lights;" if her sister is hungry, she will give to her, even from her own partially digested food; the two will often stand mouth to mouth for some minutes during this process; if she feels inclined, she will also help a sister at her toilet, and lick her with her tongue as one cow licks another. The tongue of the ant is very useful in several ways; with it she takes up liquids, and also uses it with much vigor as a washcloth. Sometimes an ant will spend a half hour or more at her own toilet, licking every part of her own body that her tongue can reach, meanwhile going through all sorts of contortions to accomplish it; she uses her feet to scrub portions of her body, not to be reached by her tongue.
But it is as infant nurse that the ant is a shining example. No mother instinct is hers, for she has yielded the power of motherhood to the exigencies of business life, since all workers are females but are undeveloped sexually. She shows far more sense in the care of her infant sisters, than the mother instinct often supplies to human mothers. The ant nurse takes the eggs as soon as laid, and whether or not her care retards or hastens hatching we know not; but we do know, that although the queen ant may not lay more than two eggs per day, a goodly number of these seem to hatch at the same time. The eggs are massed in bundles and are sticky on the outside so as to hold the bundle together. Miss Fielde says, as the eggs are hatching, one ant will hold up the bundle, while another feeds those which have broken the shell. The larvæ, when young, also hang together by means of tiny hooks on their bodies. This habit of the eggs and young larvæ is a convenient one, since an ant is thus able to carry many at a time.
The larvæ are odd looking little creatures, shaped like crookneck squashes, the small end being the head and neck and the latter being very extensible. The ant nurses, by feeding some more than others, are able to keep a brood at the same stage of development; and in a well ordered ant-nest, we find those of the same size in one nursery. I have often thought of a graded school as I have noted in ant-nests the youngsters assorted according to size.
The ants seem to realize the cost and care of rearing their young; and when a nest is attacked, the oldest, which are usually in the pupa stage, are saved first. When the larvæ are young, they are fed on regurgitated food; but as they grow older, the food is brought to them, or they to the food, and they do their own eating. In one of my nests, I placed part of the yolk of an egg hard boiled, and the ant nurses dumped the larvæ down around the edges of it; there they munched industriously, until through their transparent bodies I could see the yellow of the egg the whole length of the alimentary canal. The ant nurses are very particular about temperatures for their young, and Miss Fielde says they are even more careful about draughts. Thus they are obliged to move them about in the ground nests, carrying them down to the lower nurseries in the heat of the day, and bringing them up, nearer to the warm stones, during the evenings. This moving is always done carefully, and though the ant's jaws are such formidable nippers, she carries her baby sisters with gentleness; and if they be pupæ, she holds them by the loose pupal skin, like carrying a baby by its clothes. The pupæ look like plump little grain bags, tied at one end with a black string. They are the size of small grains of wheat, and are often called ants' eggs, which is absurd, since they are almost as large as the ant. Ants' eggs are not larger than pin points.
The ant nurses keep the larvæ and pupæ very clean by licking them; and when a youngster issues from the pupa skin, it is a matter of much interest to the nurses. I have often seen two or three of them help straighten out the cramped legs and antennæ of the young one, and hasten to feed her with regurgitated food. When ants first issue from the pupa skin they are pale in color, their eyes being very black in contrast; they are usually helpless and stupid, although they often try to clean their antennæ and make a toilet; but they do not know enough to follow their elders from one room to another, and they are a source of much care to the nurses. In case of moving, a nurse will lock jaws with a "callow," as a freshly hatched adult ant is called, and drag her along, the legs of the callow sprawling helplessly meanwhile. If in haste, the nurse takes hold anywhere, by the neck or the leg, and hustles her charge along; if she takes her by the waist the callow curls up like a kitten, and is thus more easily moved. After moving them from one chamber to the next, I have noticed that the callows are herded together, their attendants ranged in a circle about them. Often we see one ant carrying another which is not a callow, and this means that a certain number of the colony have made up their minds to move, while the others are not awake to this necessity. In such a case, one of these energetic sisters will seize another by the waist, and carry her off with an air that says plainly, "Come along, you stupid!"
Ants are very cleanly in their nests, and we find the refuse piled in a heap at one corner, or as far as possible from the brood.
If we are fortunate enough to find a queen for the nest, then we may observe the attention she gets; she is always kept in a special compartment, and is surrounded by ladies in waiting, who feed her and lick her clean and show solicitude for her welfare; although I have never observed in an ants' nest, that devotion to royalty which we see in a beehive.
Not the least interesting scene in an ants' nest is when all, or some, are asleep and are as motionless as if dead.
Leading thought—The ants are very devoted to their young and perhaps the care of them is the most interesting feature in the study of the artificial nest.
Method—Have, in the schoolroom, a Lubbock's nest with a colony of ants within it, with their larvæ in all stages, and if possible, their queen. For observing the form of the ant, pass one or two around in a vial.
1. What is there peculiar about the shape of the ant's body? Can you see which section bears the legs? Are the ants' legs long compared with her body? Can she run rapidly?
2. Look at the ant's head through a lens, and describe the antennæ, the jaws and the eyes.
3. Note how the ant keeps her antennæ in motion. Note how she gropes with them as a blind person with his hands. Note how she uses them in conversing with her companions.
4. How does the ant clean her antennæ? Does she clean them more often than any other part of her body? How does she make her toilet?
5. See how an ant eats syrup. How do ants feed each other?
6. How does the ant carry an object? How does she carry a larva or a pupa? Have you ever seen one ant carry another? If so, describe it.
7. Note the way the ants feed their young. How do they keep them clean? Does an ant carry one egg or one small larva at a time or a bundle of them? How do you suppose the bundle is fastened together?
8. Describe an egg, a larva and a pupa of the ant and tell how they differ. Do you know which ant is the mother of the larvæ in the nest?
9. Do you find larvæ of different sizes all together in your nest? Do you find larvæ and pupæ in the same group? Do the ants move the young often from one nest to another? Why do you suppose they do this?
10. Note how the ant nurses take care of the callow ant when it is coming out from the pupa skin. How do they assist her and care for her? How do they lead her around? How do ants look when resting?
11. Note where the ants throw the refuse from the nest. Do they ever change the position of this dump heap?