io8 WASP STUDIES AFIELD 



Ashmead 4 says D. tristis Dahlb. and D. minutus Fab. bur- 

 row in sand, while D. aniericamis Pack, burrows in hard clay 

 and makes burrows of "considerable depth." On D. ameri- 

 canus, one of the "tiniest of all the wasps," the Peckhams 5 

 have given us a very interesting account, and the only rec- 

 ord extant heretofore of an American species of Dio- 

 dontus. They find for this species that in most cases the 

 aphids are killed by squeezing the neck repeatedly between 

 the mandibles; in other cases the disturbance to the prey 

 is so slight that they are able to walk about as soon as re- 

 leased. The wasp never uses the sting. The nests are in 

 the ground, with some grains of dirt irregularly heaped 

 around the edges. It takes the wasp about an hour to dig 

 the nest ; she carries the earth out in her mandibles and front 

 legs, backing from the hole. The nest is not closed until the 

 provisioning is completed. The number of aphids in each 

 of six nests varied from five to forty, and sometimes the 

 aphis served as food for the mother also. 



Ceratophoms 6 tenax Fox [S. A. Rohwer]. 



At Valley Park, Missouri, on June 26, we broke of! an 

 elder stem and found this wasp in the hollow within. The 

 lower portion was crammed with twenty-five aphids, Macro- 

 siphum rudbeckiae Fitch [J. J. Davis]. The partitions were 

 of the pulverized stem. It was 4 a. m., when dawn was just 

 breaking, and we suspect this mother had spent the night 

 asleep in her nest. Another elder stem taken near by had 

 a few loose aphids of the same species in the top cells and 

 two pupal cases beneath. On July 20, two adult C. tenax 

 emerged from these. 



4 Psyche 7 : 46. 1896. 



5 Bull. Wise. Geol. & Nat. Hist. Surv. 2 : 99-106. 



6 Commonly known as Pemphredon. 



