Page:Popular Science Monthly Volume 61.djvu/348

342 time in the crop of the mother or the nurse, and then regurgitated into the mouth of the larvae. This process may be easily watched in the case of captive wasps. They nearly always make the round of the cells containing feeding larvæ some minutes after partaking of the sugar solution provided as their store of food. The animal food consists of caterpillars which have been worked by the mandibles into a mass about the consistency of marmalade.

This wasp does not sting her prey. Her habit is to seize the squirming caterpillar in her fore legs, pass it back and forth several times between her mandibles until it is quite limp and dead, and then to roll it deftly into a ball and hold it between the fore legs while she flies to the nest. There, the operation is continued three or four minutes longer, until the malaxation is complete. In distributing the food, the mass is held firmly against the ventral side of the thorax, by means of the femora of the first pair of legs and a bit partly pinched off with the mandibles. Next, the wasp inserts her head into a cell, lightly touches the larva with her antennas, causing it to stir and open its mouth, and then pushes the bit of food into the mouth with the tarsal joints of the fore legs. With the remainder, the wasp now passes to another cell and the process is repeated until the ball of food is used up. Observations on the social Hymenoptera indicate that the polymorphism occurring here is in large measure dependent on the kind of food given to the larvae. So far I have no evidence that Polistes exercises any selection in the quality or amount of food furnished the larvae which are to develop into the various members of the wasp community.

The foregoing constitute the chief activities of Polistes, but several other minor performances may be briefly noted. Among these are the stroking and rubbing movements which serve to keep the body clean. They are chiefly six in number: (1) Hanging by the four posterior legs, while doubling the first pair backward over the head and repeatedly passing them forward over the face and antennæ. The latter are thus drawn between the tibiæ and the spurs which these bear on their distal ends. (2) Drawing the first pair of legs alternately between the mandibles, and thereby removing any foreign substances accumulated by them during the first step of the process. (3) Doubling the first pair of legs as above mentioned and passing them backward over the dorsal surface of the thorax and the bases of the wings. (4) Hanging by the two anterior pairs of legs and passing the hindmost pair backward over the abdomen and the folded wings. (5) Suspending the body by the first pair of legs and drawing each of the others in turn between the tibial spurs of one of the remaining legs. (6) Drawing the wings alternately on each side between the abdomen and the hindmost leg of that side. These are sometimes gone through in the order given, but not necessarily so; some of the steps may be altogether