ODYNEItUS. 151 



In conclusion, I must add, that in most cases it is impossible 

 to determine a species in this large genus with certainty, if it is 

 not represented by more or less numerous specimens, because the 

 forms of the mesothorax are more or less variable in the same 

 species. One must also make the determination upon females, 

 the males being less distinctly characterized. They must be 

 separated by the eye to their respective females. 



Subgenus SYMMORPHUS 1 Wesm. 

 Body lengthened. Abdomen subsessile, the first segment funnel- 

 shaped, carrying a strong, transverse suture, and divided 

 on its superior face by a deep, longitudinal groove. Antennae 

 thick; those of the males simple, with no terminal hoo/,: 



The insects which enter into this group inhabit Europe and 

 America. They all present quite a similarity in form, which is 

 the reason of their name. Their body is more or less slender; 

 the clypeus is rounded, a little hollowed; the thorax is lengthened, 

 smooth, but traversed in all its length by two arcuate grooves ; 

 the post-scutel, the metathorax, and often the first segment of the 

 abdomen are rugose ; this last, while it is funnel-shaped, is also 

 truncated anteriorly before the suture and is, in consequence, less 

 petiolate than in the Nortonia. One notices among these insects 

 a particular marking ; the 3d abdominal segment often loses its 

 bordering, while the 4th preserves it, and among the females the 

 clypeus, while it does not become wholly black, takes at the 

 summit a yellow medial spot and not two lateral spots as mostly 

 in Ancistrocerus. 



The insects of this group are very easily distinguished by their 

 first abdominal segment provided with a suture and divided by 

 a longitudinal groove. They share this character with the 

 Nortonia only— the short thorax, the rounded metathorax, the 

 more pediculate abdomen, and the absence of the suture of the 

 first segment of which, suffice for a distinction. 



' In my Etudes sur la Famille des Vespides (T. Ill, p. 186), I have 

 substituted the name of Protodynerus for that of Symmorphus, under the 

 belief that the name Symmorpha had been employed during the same 

 year. But as the two terms are not absolutely identical, it seems best to 

 me to preserve the so- well-chosen name which Mr. Wesmael proposes. 



