NEST OF ANORMIS
Conformis hatched on the morning after we received it, sloughing off the skin of the egg, but remaining attached to it, and thus doubling the length of the thread by which it hung. The caterpillar was slightly separated from it, and it seemed to have no notion of feeling about for its food, eating nothing for twenty-four hours, but growing and developing nevertheless. We now piled up some caterpillars in contact with it, and it began to eat, but after its own caterpillar and as many as we dared take from anormis were gone it stubbornly refused to take soft, tender little spiders, or caterpillars out of our garden; and it perished, a victim to prejudice.
The two eggs of anormis were probably laid within a few hours of each other, since they had both hatched on the morning of the third day, and had broken from their attachment, beginning to eat at once. They cocooned on the fifth day after hatching.
We had long wished to find a nest of O. capra, and early in September fortune favored us. A neighbor of ours keeps a large tin horn hanging under the porch. One day when she wished to use it, no amount of blowing would bring forth a sound; and when she unscrewed the mouthpiece to investigate the matter, out tumbled several small green caterpillars and a quantity of dry mud. When we heard of this incident we begged that if it should be repeated the nest and its contents might be saved for us; and on the second of September we received the mouthpiece of the horn with a message to the effect that a wasp had been working at it for some days. Examination showed that there were three cells, each containing a larva and a supply of caterpillars, of which there were ten in the cell most lately formed, and only one left uneaten in the oldest. The caterpillars, all of them being alive, together with the wasp larvæ, were transferred to a place in which they could be conveniently watched. None of the caterpillars died until they were attacked. The larvæ ate all the food that was provided, the oldest one cocooning on the fourth, and the second one on the seventh of September. Of the third, we have no record, excepting that the caterpillars had all been eaten on September eighth.
We happened to be passing through our neighbor’s grounds at nine o’clock on the morning of September fifth, and calling to ask whether there had been any more visits from the wasp, we learned that capra had been seen making a mud partition in the horn on the day before. While we were speaking she arrived and entered the mouthpiece, where she remained for about ten minutes. When she departed we found that she had laid her egg, which we carried away with us, wishing to determine the length of the egg stage. This proved to be longer than that of any wasp that we had heretofore known, for not until the morning of September ninth did the larva make its appearance, the egg skin bursting and leaving its tenant free to crawl away. In other genera the egg changes into a larva imperceptibly, there being no sloughing off of the skin.
Capra, then, first finds a suitable crevice, and builds a partition across the inner end, the earth being scratched up from some dry, bare spot, and moistened in her mouth. Before gathering the ten or twelve small caterpillars that are to provision the cell, she lays her egg; and although we could not be sure, we thought that in this case as in the others it was suspended.
Unless the cell is tightly packed at the beginning, capra certainly needs the filament, for her caterpillars were so far from being reduced to a state of decent immobility that we had to press wads of cotton into the tubes in which they were kept to prevent them from wriggling out of the way of the larva. None of our larvæ, not even the one-day-old ones, were injured by their activity; but had the egg been left to its fate among them it might have perished.
Later in September we found O. vagus bringing pellets from a sharp-edged hole in the ground. Her method was to carry each load on the wing to a distance of ten or twelve inches, where it was dropped without the lively fling with which Ammophila discards her lump of dirt. The red end of a match stuck into the ground two inches away proved very disquieting to the dainty little wasp. These colored matches were a great convenience in marking nests, and as we were using them constantly, we did not guess, for a time, what the trouble was. For half an hour she went and came, circling about, alighting upon plants, and seeming entirely absorbed in examining them with the minutest care, even alighting upon our hands with most engaging friendliness, but pretending all the time that the nest was naught to her. When the offending object was removed she hurried in at once and resumed her work. The storing was not begun until the next morning, when she took in six caterpillars of very different sizes, at intervals of from ten to twenty minutes, and then filled the hole. We hoped to find the little chamber arranged as in reniformis, but had not skill enough to excavate in such a way as to show the internal plan. It is remarkable that this genus, with only one set of tools for all its species, has worked out such different styles of architecture, the ground nests bearing no resemblance to those cut out of woody stalks; and its flexibility is shown in the use of empty snail shells by a foreign species, as well as by capra’s habit of partitioning off convenient crevices found ready made.
The prettiest nests that we have seen in stems are those of Plenoculus peckhamii, which separates its cells, not by solid partitions, but by numerous granules of earth, which are used by the larvæ for forming the case of the cocoon. One raspberry stalk that we opened had at the bottom six of these mud cocoons, and above these three larvæ eating, each in its own compartment, the provision in this case consisting of immature bugs of the genus Pamera. Sometimes the stalk which is being filled by Plenoculus attracts the fancy of a bee or of another wasp, as is shown by the upper cells being filled by Osmia or Crabro, or sometimes Plenoculus builds above the bee cells. When a number of wasp eggs are placed in a plant stem, the last one laid is the first to hatch. The different habits of the Hymenoptera in this respect are very interesting. In the case of Ceratina dupla, the small carpenter bee, the egg first laid hatches first, those above following in regular order. The lower ones wait patiently in their cells until the one in the top cell has matured, and then they all come out at once. When two species occupy the same stalk, the lack of adjustment probably results in the destruction of those lower down, excepting in the case of the cuckoo flies, which have acquired the habit of gnawing their way out at the side of the stem.