no. 2173. A REVISION OF THE BEMBICINE WASPS— PARKER. 135 



the open spaces entirely free from vegetation, but their burrows may 

 be found almost anywhere among the clumps of grass and even under 

 the trees wherever the sand is free from leaves or not hidden by 

 foliage. Although a high wind, when the sand is dry or a violent 

 rain-storm, invariably alters in no small measure the surface of the 

 naked sand, nevertheless such changes in no way discourage these 

 energetic little insects or even seriously interfere with their prosperity. 



On June 17 the wasps were found in great numbers flitting about 

 over the sand and many were already at work on the construction 

 of nests. The great majority, however, at this time were males, 

 from which fact it seems that the males emerge somewhat earlier 

 than the females. A number of pupae were digged out of the sand 

 and the insects permitted to emerge in the laboratory. In all 10 

 insects were secured in this way and all were females. In searching 

 the sands from day to day many emerging wasps were digged out, 

 but only a very few of these were males, and my records show that 

 not a single male was thus discovered after the 1st day of July. 



Mating occurs immediately after the female has emerged. The 

 fact that the male emerges in advance of the female appears to be a 

 provision of nature to insure the fertilization of all females. The 

 males are constantly searching the sands for the emerging females, 

 and a female is not long above ground before she is discovered by a 

 passing male and fertilized. The female is usually found and seized 

 by a male before she has made any attempt to fly, and a fierce but 

 brief struggle precedes copulation, the pair rolling about on the sand 

 or in some instances rising into the air. Copulation requires but a 

 brief time, about half a minute, and the male seems capable of fer- 

 tilizing a number of females. All data secured tends to show that 

 copulation occurs but once. While the females are digging their 

 burrows and searching the sands for food for their young they are 

 continually pestered by the roaming males, every one of which in 

 passing a busy female either hovers about her for an instant or 

 pounces upon her back. In the majority of such cases the male 

 retains his hold but momentarily, apparently realizing very quickly that 

 he has made a mistake; in others a struggle ensues upon the sand and 

 occasionally the male will retain his position on the back of the female 

 for some time, but in all of these cases, and hundreds were observed, 

 not a single mating was effected. At the close of the period of 

 investigation very few males were in evidence and the females in 

 great numbers were digging their burrows in peace. 



The nest is a simple unbranched tube and a single larva is reared 

 in each. The young is reared at the extreme end of the burrow, 

 which is enlarged somewhat to form a brood chamber. These bur- 

 rows are from 8 inches to 1 foot in length from end to end and the 

 brood chamber is from 3 to 6 inches below the surface of the sand. 



