ANTS AND WASPS 65 



of an old-fashioned looking-glass, in the folds of a 

 piece of paper that had fallen behind some books, in 

 hollow reeds used as thatcb, and in the barrels of a 

 pistol that was hanging invitingly on a post. In all 

 these cases accident furnished the insects with cavities 

 ready made, and saved them the trouble of excavating 

 their own burrows. 



These wasps are also sometimes seen in windows, 

 buzzing about, apparently endeavouring to discover why 

 a medium so transparent as glass should yet be able 

 so successfully to bar their exit into the outer world. 



The abdomen of an Odynerus is of a very curious, 

 shape (Fig. 24), In all the wasps, the first segment 

 seems more or less like a cap on the 

 succeeding ones, but this is much more 

 markedly the case in the solitary than 

 in the social species. In the genus 

 Odynerus the abdomen bears a ludicrous 

 resemblance to a peg-top surmounted 

 by a polo -cap which is rather too 

 small for it. The second segment is 

 of enormous size compared with the 

 succeeding ones, and being very convex $w- 24. Abdomen of 

 above, forms the head of the top. This 

 segment is black, except the hind border, which is 

 yellow, and the succeeding segments are more or less 

 deeply margined with the same colour. The basal 

 segment, i.e., the cap, is also furnished with a yellow 

 marginal band, the shape of which is an important 

 aid in the identification of the species. The folded 

 wings and the top-shaped abdomen are quite sufficient 

 to enable any one to recognise a sand-wasp. 



