Rubrocinctum was more conveniently studied, and through July and August we watched the comings and goings of these little wasps. They were very good-tempered, never resenting our close proximity nor our interference with their housekeeping. By working hard they could prepare a nest, store it with spiders, and seal it up all in the same day. This we have seen them do in several instances. In other cases the same operation takes three or four days. In the second summer that we worked with them we found one very energetic mother that stored four nests in one day. It had rained hard on the twenty-sixth of July, and no wasp works in such weather. On the afternoon of the twenty-seventh we took a straw just as the little mother was bringing in a spider. We opened it and found that the innermost cell contained eight Epeirids, with an egg on the abdomen of the last one taken in; the second cell was provisioned with ten spiders, with the egg on the seventh, so that three had been brought in after it was laid; the third cell had the egg on the last spider, as did also the fourth. All of these eggs hatched on the twenty-ninth,—the two outer ones, that were laid last, between eight and nine o’clock in the morning, and the two that were laid earlier between two and three in the afternoon. This was the biggest day’s hunting that we have ever recorded for any of our wasps.
With both species (T. rubrocinctum and T. albopilosum), when the preliminary work of clearing the nest and erecting the inner partition has been performed by the female, the male takes up his station inside the cell, facing outward, his little head just filling the opening. Here he stands on guard for the greater part of the time until the nest is provisioned and sealed up, occasionally varying the monotony of his task by a short flight. As a usual thing all the work is performed by the female, who applies herself to her duties with greater or with less industry according to her individual character; but the male doubtless discharges an important office in protecting the nest from parasites. We have frequently seen him drive away the brilliant green Chrysis fly, which is always waiting about for a chance to enter an unguarded nest. On these occasions the defense is carried on with great vigor, the fly being pursued for some distance into the air. There are usually two or three unmated males flying about in the neighborhood of the nests, poking their heads into unused holes, and occasionally trying to enter one that is occupied, but never, so far as we have seen, with any success, the male in charge being always quite ready and able to take care of his rights. The males, however, made no objection when strange females entered the nest, as they sometimes did by mistake, nor did the females object to the entrance of a strange male when the one belonging to the nest happened to be away; but in such cases the rightful owner, on his return, quickly ejected the intruder. We often amused ourselves, while we were watching the nests, by approaching the little male, as he stood in his doorway, with a blade of grass. He always attacked it valiantly, and sometimes grasped it so tightly in his mandibles that he could be drawn out of the nest with it.
When the female returns to the nest with a spider the male flies out to make way for her, and then as she goes in he alights on her back and enters with her. When she comes out again she brings him with her, but he at once reënters, and then, after a moment, comes out and backs in, so that he faces outward as before.
In one instance, with rubrocinctum, where the work of storing the nest had been delayed by rainy weather, we saw the male assisting by taking the spiders from the female as she brought them and packing them into the nest, leaving her free to hunt for more. This was an especially attentive little fellow, as he guarded the nest almost continuously for four days, the female sometimes being gone for hours at a time. On the last day he even revisited the nest three or four times after it had been sealed up.
It is upon the female that the heaviest part of the work devolves. As soon as she has put the nest in order she begins the arduous task of catching spiders wherewith to store it. It usually takes her from ten to twenty minutes to find a spider and bring it home, but she is sometimes absent for a much longer time. When the spider has been carried to the nest the process of packing it in begins. This occupies some time, and apparently a good deal of strength,—the female pushing it into place with her head, totally disregarding its comfort, all the spiders that are caught being pressed and jammed together into a compact mass. While she is busied in this way she makes a loud cheerful humming noise. The number of spiders brought seems to depend upon their size, in which quality they vary greatly, the largest ones being six or eight times as large as the smallest. Rubrocinctum fills her nest with from seven to fourteen, while the larger albopilosum brings as many as twenty-five or thirty. Those that we examined represented many different genera, and even different families, although they were usually orb-weavers.
In a number of cases, during the first summer, after several spiders had been stored, we gently drew them out with a bent wire. In one nest in which there were five spiders, we found, two hours after they had been stored, that three were alive and two were dead. In another, which the wasp had just begun to seal up, were ten spiders. Three of these were injured in being drawn out. Of the remainder four were alive and three dead. On the anterior part of the dorsum of one of the living spiders was the egg. It had probably been fertilized as the female carried the male into the nest on her back.
When we discovered rubrocinctum in the straw-stack, we made many observations as to the position of the egg and the number and condition of the spiders. We found that the egg was always placed either on the side or the back of the anterior part of the abdomen. The number of spiders stored was, as we have already stated, from seven to fourteen. A fact that interested us greatly was the remarkable accuracy shown by the wasp in never selecting too large a spider for the calibre of the straw. Oftentimes it was an extremely close fit, but it could always be squeezed down. When they nested in posts they used at times much larger prey. Unfortunately we never saw this species capture its prey, nor could we prevail upon it to sting in captivity, but the number of spiders that we found in straws was so large as to afford abundant evidence concerning the degree of surgical skill possessed by the wasps. P. marginatus and P. scelestus, in overpowering their large fierce Lycosids, must sting when and where they can, but most of the spiders taken by rubrocinctum are inoffensive creatures, and there is so little need to be careful or adroit in dealing with them that she has time and opportunity to sting the exact spot that will give the best results.
