28 BEES AND WASPS [OH. 



moments, then, in order to afford a clear path along 

 which to kick the loosened sand, she elevated her 

 abdomen over her thorax, holding the fly up in the 

 air impaled on her sting at the tip, and with her 

 hind legs scattered the little heap that had been 

 gathered by the front feet. I watched the whole of 

 this manoeuvre through a strong lens. 



Among our British Sphegidae the genus Crabro 

 is represented by the greatest number of species, and 

 may therefore claim some notice in these pages. The 

 insects comprised in this genus differ widely from one 

 another in superficial appearance, some being entirely 

 black, while others are conspicuously banded with 

 yellow and a few with red : in size too they vary from 

 nearly three-quarters of an inch to less than a quarter 

 of an inch in length. They may, however, be recog- 

 nised without much difficulty by the peculiar arrange- 

 ment of the cells into which the forewings are mapped 

 out by the veins or nervnres, if two other fairly obvious 

 features present in two small genera which share this 

 peculiarity be taken into account. In any of the 

 Hymenoptera dealt with in this volume it will be seen 

 that there are in the fore wing four "nervures" which 

 start from the attachment of the wing to the body 

 and run out horizontally towards the tip of the wing : 

 the foremost of these "nervures" forms the front 

 margin of the outstretched wing and is known as 

 the costal nervure: very close behind it and almost 



