THE BEMBICENE WASPS 33 



pressure of the wasp pushing up from beneath, or occasion- 

 ally the wasp itself will come pushing its way out backwards 

 through the loose soil, emerging not a little dishevelled, and 

 shake itself vigorously to free it from the clinging dirt, pre- 

 cisely as a dog shakes himself upon coming out of his bath. 

 She then proceeds to dig out and sweep back the dirt she has 

 brought to the top of the hole. But at these resting-periods 

 mentioned above, no such movements are seen for days 

 at a time, so we suspect that she is merely resting and 

 enjoying the security of her home. But is she only 

 gratifying a whim, or may she be waiting for the matura- 

 tion of her ova or some other physiological phenomenon? 

 The population diminishes at the end of the season; perhaps 

 the old adults simply go off and die after they have com- 

 pleted their season of nidification. 



On this occasion we might mention one other form of 

 mortality which is yet unexplained. Early each year, when 

 digging out the burrows of various species, we come upon 

 a few subterranean chambers, which have never been 

 opened, containing a dead Bembix. Whether these are 

 young wasps which have safely arrived at maturity but have 

 died before emerging, as often happens in other species, or 

 whether they are parent wasps which have died while in 

 the burrows, we had no way of ascertaining. 



The contents of a few nests have puzzled us utterly. One 

 hole 5 had long roused our curiosity as we watched and 

 waited for its permanent sealing. Finally, one evening at 

 twilight, we broke open its temporary closure and found 

 therein six B. nubilipennis ready to spend the night. Two 

 of these were captured and proved to be females. Since we 

 now know of the male priority of emergence and disappear- 

 ance, we feel fairly safe in assuming that all of these were 



5 The Sleep of Insects. Ann. Ent. Soc. Amer. 9 : 240. 1916. 



