Chapter XI
WORKERS IN CLAY
THE nests of Pelopæus cœruleus and Pelopæus cementarius, our two mud-daubers, are common under eaves and in other sheltered places, and many a country boy on opening them has been astonished to find that they do not contain wasps, but are crammed with spiders. Let them alone, however, and the wasps will arrive, for somewhere in the mass is an egg; and when it hatches the spiders will serve as breakfast, dinner and tea for the larva, until the change from the Arachnida to the Hymenoptera has been accomplished. Poor spiders! it is a wonder that there are any left, such thousands and tens of thousands are destroyed by these tremendously energetic enemies.
Of what is Pelopæus thinking as, humming loudly, she jams her paralyzed and benumbed victims into her little cylindrical tubes? If only we could get inside of that little head! If only we could be wasps for a day, and then come back and tell about it, how much vain speculation would be saved! We can understand her when she soars gayly into the blue, the sunshine flashing from her brilliant wings; we too have felt the delight of health and freedom. She is still comprehensible when, at the close of day, she and her sisters quarrel for the favorite sleeping-places among the carvings of the porch pillars; but we cannot follow her mental processes when, at the moment of building, she surrenders herself to the mysterious sway of instinct, doing she knows not what, but doing it joyously, and preserving through it all the precious possession of her own individuality. Every aspect speaks of pleasure as these wasps gather at well or spring, and, singing contentedly, stand on their heads to gather their loads of mud. Briskly and gayly they fly back and forth, pausing at the nest long enough to pat the soft building material into shape. A single load makes half a ring at the larger part of the nest or a whole one at the bottom; and since one dries before the next is put on, the contour of each ring is visible when the tube is done, giving a very artistic effect. This is only accident, however; the wasp cares nothing about the beauty of the structure, for her next step is to daub the whole with lumps of mud, the walls being thus thickened and strengthened. About forty loads are necessary for each cell, and to build and provision one is a good day’s work.
It is strange enough that with no one to teach her Pelopæus knew how to make her cell; but now she must do her hunting, and it is stranger still that she should be impelled to catch nothing but spiders. How does she know a spider from a fly, and why should she prefer one to the other? Not so unreasonable as some wasps, however, she demands nothing further than that her prey shall belong to this great group, and passes lightly over differences of species and genera. Her powerful sting fits her to cope with anything she may meet; but as the size of the cell must be taken into consideration, and the victim must be carried home on the wing, she is on the lookout for something not too large. Here then she ceases to be an automaton, and to some extent makes use of her wits.
How does Pelopæus seize her spider? When and how many times is it stung? Is the wound given with discrimination, a certain point in the ganglion being pricked, so that the spider may be paralyzed, but not killed? Is there any malaxation?
These were important questions to us, and we were therefore greatly excited over our first hunt. One of the blue wasps came flying along, alighted on our cottage wall, and began her search, creeping into corners and cracks and investigating cottony lumps of web. In a few moments a small Epeira strix (the only species to be found on the cottage) was dislodged, and at once dropped to the floor of the porch. The wasp paid no further attention to it, but went on with her search. Three more spiders, one after the other, were disturbed and dropped to the floor without being followed. The fifth one discovered was a little larger than the others, and was seized by the jaws and first legs of the wasp before it had time to escape. It was then rolled into a ball, or at least so it appeared, and stung, then rolled a little more and stung again, and then carried off. We had scarcely drawn breath after this performance when a second wasp appeared. This one dislodged two spiders, and then caught a third, which was seized and stung without any rolling, and then instantly borne away. A third wasp seized the first spider that she found, and started on her flight at the same moment, stinging it on the wing.