Our new–found wasp stayed only a moment in her nest, although, as we afterward found, it was long enough for her to lay her egg on the fly. When she came out she quickly smoothed the sand over the spot with her head and legs so that there was nothing to mark the nest, and flew away. In three minutes she returned with another fly. She alighted two or three inches away, and scratched for an instant, but quickly saw her mistake, and found the right spot.
Again and again the pretty little worker went and came, while we sat watching close by, admiring her deft handiwork in opening and closing the nest and wondering at the ease with which she found it at each return. There was nothing tiresome or dilatory about this species, and within twenty minutes we had seen six flies stored up. The nest was closed and the place smoothed over every time before she went away, but when she entered she left the door open behind her. We once tried to make her drop the fly, but when disturbed she flew up and alighted on a plant near by, keeping her hold on it. The whole performance was brisk and business–like, but without the feverish hurry of Ammophila and Pompilus.
After the sixth fly was taken in we were afraid to let her go again, thinking that the nest must now be completely provisioned, and that she would not return. She was such a charming little wasp, scarcely bigger than a fly herself and yet so useful in her industry, that we hated to disturb her; but as we were obliged to have her for identification we first caught her, and then opened the nest. It contained only the flies that we had seen taken in, the egg being attached to the one lowest down, on the left side, between the head and the thorax. It was long and cylindrical. The flies were dead, but showed no marks of violence. We learned later that it takes Oxybelus two hours to make her nest so that this one must have been prepared the day before.
The egg, which was laid just before nine o’clock on the morning of August seventh, hatched at a little after nine on the morning of August eighth. The larva began to eat at once, and devoured all the inside of the thorax and abdomen of the fly to which it was attached, in the first twenty–four hours. On August twelfth it had reached the sixth fly, and we supplied it with three more. On August fourteenth these were gone, and we again replenished its larder, this time with two flies. The larva had partly eaten these when something went wrong. Its appetite failed, and on August sixteenth it died.