SOME GRAVE DIOGEES. 109 



The nests of our species are all deep, tortuous, and very 

 •difficult to excavate. We have never succeeded in finding their 

 pockets and yet, for various reasons, we feel perfectly certain 

 that nigrescens, deserta, and clypeata are like C. orna- 

 ta in provisioning, successively, a number of cells which lead 

 out of the main gallery. When one of these cells is filled with 

 food and the egg deposited, it is probably closed up and thus 

 separated from the runway. From our experience late in the 

 season with the nests of another wasp (Astata unicolor) we are 

 inclined to think that we made a mistake in looking for pockets 

 at the lower end of the tunnel. Had we searched higher up, at 

 the point of the curve, we might have found them, the lower 

 part of the gallery probably being designed merely for a dwell- 

 ing place for the mother of the family. 



But although we did not get distinct pockets we found, in at 

 least one nest, a supply of food that would have far exceeded 

 the wants of a single larva. We did not succeed in finding dif- 

 ferent eggs on different groups of beetles but in a nest into 

 which the wasp was still carrying food we found a half grown 

 larva which was identified as being hers. The fact, too, that a 

 wasp occupies a nest for so long a time as ten days or two weeks 

 points to the conclusion that she uses it for a number of eggs 

 which are laid at intervals. 



Cerceris digs her nest, deep ag it is, all at once. In this she 

 is a contrast to her near relatives of the genus PhilantJms who 

 busy themselves for an hour or so every morning with fresh ex- 

 cavations. 



Cerceris clypeata Dahlborn. 



Plate I., fig. 8. 



On the eighth of July the weather was so warm and bright 

 that we went down to the garden at half past eight o'clock, 

 knowing that it was rather early but hoping that the hot 

 sunshine would tempt the wasps to industry. We had walked up 

 and down several times when suddenly, right in the pathway, a 

 nest appeared. A great quantity of loose earth had been taken 



