324 WASP STUDIES AFIELD 



not oviposit at the conclusion of the provisioning, as do 

 other species, but whenever it suits her fancy or physi- 

 ology. We sometimes find the little egg swinging from the 

 wall on its thread when the provisioning is only begun or 

 half done. 



Among the St. Louis population of dor sails we have 

 found only the one species of caterpillar used as prey, viz., 

 the Hesperid larva, Pholisora catullus [Drs. Barnes and 

 McDunnough], while Iseley has found two species of Lepi- 

 dopterous larvae used by the Kansas O. dorsalis, the species 

 mentioned above and Pyrgus tesselata. 5 



We are not positive that O. dorsalis always sleeps in her 

 burrows, but we have found her in the unfinished holes at 

 twilight and on dark, cloudy days a sufficient number of 

 times to make us certain that at least the females do so 

 frequently while the digging is in progress. Of course 

 the problems remain of where the males sleep, and where 

 the females find shelter when they have not open holes at 

 their disposal. 



It has always seemed to us remarkable that the nests of 

 O. dorsalis are not more often ravaged by parasites or ene- 

 mies, since the owner always leaves the burrows wide open 

 during her long absences. Yet we believe she suffers less 

 at the hands of such impostors (at least in the nests which 

 have come under our notice) than do some of her sister 

 species which always close their burrows behind them with 

 such exacting care. 



From one open hole we saw an O. dorsalis emerging 

 and watched her closely to ascertain her method of egress. 

 Imagine our surprise when we saw her carry out a P. catul- 

 lus caterpillar in her front and middle pairs of legs, pause 

 at the brink of the hole for several seconds to adjust the 



5 We have observed O. dorsalis in three widely separated areas but 

 never yet have we found her using caterpillars other than Pholisora 

 catullus. 



