When a female returns with her load she usually hunts about for a few moments before finding her nest, sometimes entering, first, two or three that are empty or are occupied by other wasps; but we do not wish to cast any reflection upon the sense of locality of a creature that is able to find one particular straw out of the many thousands in an expanse of stack twenty feet high by twelve wide. We ourselves can testify, from experience, to the extreme difficulty of the task.
After the storing process is completed the female seals up the nest with mud. In the case of one rubrocinctum that we were watching, she began to close the opening at four in the afternoon and finished her work just thirty minutes later. In this time she made ten journeys for mud, bringing it in pellets in her mandibles. In another case, also a rubrocinctum, the female, after bringing so many spiders that the cell was full up to the very door (which we saw in no other case), went away without closing it, and never returned. The male seemed uneasy at her conduct, and several times flew away, staying an hour or two and then returning; but after a time he too deserted the nest. Whether some evil fate overtook the female or whether there was some failure of instinct on her part, can only be conjectured; but the latter hypothesis is not untenable, since out of seventy-six nests that we had under observation seven were cleaned out and prepared and were then sealed up empty. We have often found similar cases among the nests of the blue mud-dauber wasps, where it is not a very uncommon thing for the absent-minded females to build their pretty little cylindrical nests with infinite care and patience, and then to seal them up without putting anything inside.
Cocoons of rubrocinctum that were gathered in the month of August remained over the winter and hatched in May and June.
Almost as interesting as rubrocinctum is the slightly larger species, T. albopilosum. This wasp has a great liking for the posts that support the balcony of our cottage, a preference that is very convenient for us, as it enables us to sit in the shade and watch their doings at our ease.
One afternoon as we sat, literally, at our posts, a female of albopilosum came humming along, looking very important and energetic, as though she had planned beforehand exactly what to do. She entered an empty hole, head first, and at once began to gnaw at the wood, kicking it out backwards with considerable violence. After a few minutes she changed her method of work, and began to carry out loads of wood dust in her mandibles, dropping it in little showers just outside the nest, and then hastening back. In forty minutes she carried out, in this way, upwards of fifty loads. She then flew away, but returned in ten minutes with a male. She alighted, he took his place on her back, and they went in together.
After a time they came out and both flew away, but the next morning they came back and the nest was stored.
