158 HYMENOPTERA ACULEATA. 



small lobe at the basal angle ; abdomea sub-elongate, tlie 

 basal segment narrower than the second, not sharply 

 truncate at the base as in Ve--<2}a, genital armatui-e of the 

 cJ with the stipites elongate and more or less Sjiiniform. 



There are two genera recorded from this country, which 

 may be distinguished thus : — 



1. Abdomen not, or scarcely, petiolated, basal seg- 



ment more than half the width of the second . Odtnerus. 



2. Abdomen petiolated, basal segment not half so 



wide as the second Eumenes. 



ODYNERUS, Latr. 

 Easily known from Eumenes, the only other British 

 genus of this family, by the comparatively wide first 

 segment of the abdomen, which has no elongate petiole 

 as in that genus. The British species are clearly divisible 

 into the three sections defined by Wesmael, viz., Hoplopus 

 Ancistrocents and Symmorphus ; there is a fourth section 

 defined bySaussure, viz., Leionotus, but hitherto there has 

 been no authentic record of it having been found in this 

 country. There are twelve British species, but the Palse- 

 arctic species are very numei'ous, and their number probably 

 quite problematical, as there is a great general resemblance 

 between them all, and great care and study is necessary to 

 differentiate the species with certainty. One of the most 

 important characters lies in the form of the second ventral 

 segment of the abdomen, this has a transverse sulcature at 

 some little distance from the base, crossed by a series of 

 carinae ; the length of these carinse and the shape of the seg- 

 ment offer very constant and reliable characters. Several 

 of the species are subject to the attack of the parasitic 

 genus Chrysis. The following is the table of the British 

 species : — 



(10) 1. Basal segment of abdomen without 

 a transversed carina at the base ; 

 antennas in the rj spirally rolled 

 at the apex (Subg. Hoplopus, 

 Wesm.). 



