342 POPULAR SCIENCE MONTHLY. 



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 larvae 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 squirm- 

 ing caterpillar in her fore legs, pass it back and forth several times be- 

 tween 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 antennae. The latter are thus 

 drawn between the tibiae 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 back- 

 ward 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 hind- 

 most leg of that side. These are sometimes gone through in the order 

 given, but not necessarily so; some of the steps may be altogether 



