Chapter II
AMMOPHILA AND HER CATERPILLARS
BEFORE we had worked long on our Vespa family we were beguiled by tempting opportunities into running after the solitary wasps. The solitaries, so far as species are concerned, are immensely more numerous than the socials; but they have only two sexes, and the males and females usually see but little of each other after the mating is over, although we occasionally find them living happily together until the end of the season. In the early summer they begin to emerge from the nest in which the eggs were laid the year before. Solitary indeed they come into the world, the generation that gave them birth having perished in the fall. For a time their career is one of unmixed pleasure, and yet, free and unguided though they are, basking in the sunshine, feeding on the flowers, or sleeping at night under some sheltering leaf, they are hourly acquiring experience, so that when the cares of life descend upon them they are no longer creatures of mere instinct. With these sobering cares an almost absurdly heavy sense of responsibility for future generations transforms the hitherto happy-go-lucky females into grown-up wasps with serious views on marketing and infant foods. Each one makes a separate nest and provisions it by her own labor; and in many cases a new nest is made for each egg. There is no coöperation among them; although in certain genera, as Aphilanthops and Bembex, a number of individuals build close together, forming a colony. The nests may be made of mud, and attached for shelter under leaves, rocks, or eaves of buildings, or may be burrows hollowed out in the ground, in trees or in the stems of plants. The adult wasp lives upon fruit or nectar, but the young grub or larva must have animal food; and here the parent wasp shows a rigid conservatism, each species providing the sort of food that has been approved by its family for generations, one taking flies, another bugs, and another beetles, caterpillars, grasshoppers, crickets, locusts, spiders, cockroaches, aphides, or other creatures, as the case may be.
When the egg-laying time arrives the female secures her prey, which she either kills or paralyzes, places it in the nest, lays the egg upon it, and then, in most cases, closes the hole and takes no further interest in it, going on to make new nests from day to day. In some genera the female maintains a longer connection with her offspring, not bringing all the provision at once, but returning to feed the larva as it grows, and leaving the nest permanently only when the grub has spun its cocoon. The males never acquire this interest, so admirable for the development of character, and aid little, if at all, in the care of the family. The egg develops in from one to three days into a footless, maggot-like creature which feeds upon the store provided for it, increasing rapidly in size, and entering the pupal stage in from three days to two weeks. In the cocoon it passes through its final metamorphosis, emerging as a perfect insect, perhaps in two or three weeks, or, in many cases, after the winter months have passed and summer has come again.
Most graceful and attractive of all the wasps—“taille effilée, tournure svelte,” as Fabre describes them, the Ammophiles, of all the inhabitants of the garden, hold the first place in our affections. Not so beautiful as the blue Pelopæus, nor so industrious as the little red-girdled Trypoxylon, their intelligence, their distinct individuality, and their obliging tolerance of our society make them an unfailing source of interest. They are, moreover, the most remarkable of all genera in their stinging habits, being supposed to use the nicest surgical skill in paralyzing their caterpillars; and few things have given us deeper pleasure than our success in following the activities and penetrating the secrets of their lives. In our garden we have two species of Ammophila, urnaria Cresson, and gracilis Cresson, both of them being very slender-bodied wasps of about an inch in length, gracilis all black, and urnaria with a red band around the front end of the abdomen. A. polita and A. vulgaris, which look much like urnaria, are common in the sandy fields west and south of Milwaukee.
AMMOPHILA URNARIA CARRYING CATERPILLAR TO NEST
During the earlier part of the summer we had often seen these wasps feeding upon the nectar of flowers, especially upon that of the sorrel, of which they are particularly fond; but at that time we gave them but passing notice. One bright morning, however, we came upon an urnaria that was so evidently hunting, and hunting in earnest, that we gave up everything else to follow her. The ground was covered, more or less thickly, with patches of purslain, and it was under these weeds that our Ammophila was eagerly searching for her prey. After thoroughly investigating one plant she would pass to another, running three or four steps and then bounding as though she were made of thistledown and were too light to remain upon the ground. We followed her easily, and as she was in full view nearly all of the time we had every hope of witnessing the capture; but in this we were destined to disappointment. We had been in attendance on her for about a quarter of an hour when, after disappearing for a few moments under the thick purslain leaves, she came out with a green caterpillar. We had missed the wonderful sight of the paralyzer at work; but we had no time to bemoan our loss, for she was making off at so rapid a pace that we were well occupied in keeping up with her. She hurried along with the same motion as before, unembarrassed by the weight of her victim. For sixty feet she kept to open ground, passing between two rows of bushes; but at the end of this division of the garden, she plunged, very much to our dismay, into a field of standing corn. Here we had great difficulty in following her, since, far from keeping to her former orderly course, she zigzagged among the plants in the most bewildering fashion, although keeping a general direction of northeast. It seemed quite impossible that she could know where she was going. The corn rose to a height of six feet all around us; the ground was uniform in appearance, and, to our eyes, each group of cornstalks was just like every other group, and yet, without pause or hesitation, the little creature passed quickly along, as we might through the familiar streets of our native town.