242 WASP STUDIES AFIELD 



food upon the emerging wasp and its resultant ability to 

 grapple in turn with large prey. Then when the interme- 

 diate forms had dropped off, there would be left only the 

 two distinct forms, A. pictipennis, which uses one medium- 

 sized caterpillar, and A. procera, which uses one large one, 

 with the instincts of nest-building and carrying prey not at 

 all changed. 



A. procera seems to be one of our most husky species for 

 enduring the cold of autumn. On October 28, at Clifton, 

 Illinois, we took three specimens and saw many others on the 

 bluffs of the Mississippi. The days were sunny, but the 

 nights were very cold. 



They have many times been seen feeding on the flowers of 

 white snakeroot and Melilotus, and the species is reported 

 by Banks to frequent the flowers of Ceanothus. The only 

 enemy mentioned for this wasp is the twisted-wing parasite 

 recorded by Pierce. 



The behavior of this insect has been worked out by Hart- 

 man. 17 He finds her very tolerant of human company, 

 which our Missouri wasps are not. The work of excavating 

 occupies about thirty-five minutes ; the gallery is nearly verti- 

 cal at the top and runs down in a gentle curve until it be- 

 comes almost horizontal where it widens out into a spacious 

 pocket. The large individuals, he says, store but one im- 

 mense green tomato caterpillar, and the smaller ones sev- 

 eral caterpillars. He tells how a pair of females had a duel 

 over a caterpillar, and relates various pretty incidents. 



After the custom of many wasps of her group, A. procera 

 does not sleep in individual nests, but assembles in small 

 groups to sleep. The reason for this gregariousness in sleep 

 has not been ascertained. We watched one such group of 

 these wasps which returned, night after night, to the same 

 dried stem, about three feet tall, which stood in the midst of 

 abundant green vegetation. Their mandibles were locked 

 17 Bull. Univ. Tex. 6: 11-20. 1905. 



