28 Some Solitary Wasps of Texas. 



lays a single egg in the empty nest and waits for the larva to hatch 

 before she begins to lay in a supply of flies. This explains her 

 leisurely behavior on the third and fourth days of the nest, when 

 she digs spasmodically or even visits the nest without working at 

 all. 



After the long and slender egg (six mm. in length) has hatched, 

 the larva is kept well supplied with flies. These belong to any of the 

 common species in the woods, Musca domestica, Calliphora voinito» 

 ria and especially the large Volucella escurieus, Fahr. var. Mexicana, 

 Macq. She does not confine herself to a single species of fly as does 

 Thyreopus argiDs, which preys on a species of Dolidioptis. The size 

 of the fly is not graduated to the size of the larva, as is said to be 

 the case with Bembex, but it appears that the first fly met with, large 

 or small, is captured and brought home. The wasp carries the fly 

 with her middle pair of legs and on entering passes it deftly back 

 to the last pair. This habit seems to be characteristic of the Bera- 

 becids in general. 



The larva is fed for at least eleven days ; I observed one individual 

 continue this from Aug. 17th to Aug. 28th. During this time, 

 twenty-four or more flies had been brought in, since, when I dug 

 up the nest, I found the large larva, (which spun its cocoon the 

 next day) surrounded by the remains of empty dipterous skeletons: 

 24 heads, 11 thoraces, 8 abdomens and many wings, the hardest 

 parts of the different species of flies having been left. Fig 15 rep- 

 resents a pupa surrounded by the remains of flies in the sand. 



M. Carolina shows a remarkable variation in habit in that she 

 sometimes closes her nest before she flies away, sometimes leaves it 

 open and this applies to some individuals as well as to the species as 

 a whole. Of the eleven specimens that I observed, six closed the nest 

 carefully each time they left it; two always left theirs open; two 

 closed theirs once or twice in a slip-shod manner leaving it open at 

 all other times ; and one closed hers carefully until she begun to car- 

 ry in flies, when it was never again closed until the larva was full 

 grown. 



Each individual performs the final closure with scrupulous care, 

 the whole tunnel being filled with sand and the surface smoothed 

 over in the radius of a foot. One wasp kept returning to the nest 

 occasionally for several days to throw more sand over the entrance 

 to her old nest until she had kicked up a pile of sand three inches 

 deep. 



