170 HTMENOPTERA OP AMERICA. [PART I. 



by its smaller size, its less angulate metathoracic plate, by the 



narrow border of the firs1 segment, by the transparent wings and 



quite different livery: from the 0. albophaleratus by its yellow 



ornaments; its shorter thorax, a little less strongly punctured, 



its abdomen Laving more punctures, its antennae mere colored, 



and the size a little larger : from the 0. unifasciatus and cam- 



,• by its metathoracic plate bordered throughout by sharp 



ridges and by the border of the 2d segment which is not rugose. 



But above all it might be confounded with the 0. birenimacu- 



latus. It is distinguished from it by the less rich livery, by the 



lar border of the first segment, by the very much less gross 



form, by the much smaller size, etc. Compare these two species 



ully. 



Hab. The United States. New York. Connecticut. Illinois. 

 (1" 9,5 £.) 



Observation. — This species is the American representative of 

 the 0. renimacula and it appears to me to differ from this species 

 only by the rather less defined angles of the prothorax and by the 

 metathoracic plate, which is not striate. 



1 possess a very small individual, 9 (long. 8 mm.), which per- 

 haps indicates the existence of another allied species. The thorax 

 is a little more lengthened, the first segment of the abdomen is 

 divided by a feeble groove, the clypeus offers but two yellow 

 dots toward the base, and the metathoracic ridges are marked by 

 two little yellow lines. (Connecticut, Mr. Edw. Norton.). 



I possess also many more little males which I cannot but 

 ascribe to this species and which, in fact, do not present any 

 difference from the males of the normal size, but in being much 

 smaller, and that some of the punctures of the first segment of 

 the abdomen are'a little stronger. Length, 8.5 mm.; wing, 7. 



These specimens have no separate spots on the 2d abdominal 

 segment. The 1st segment carries a regular border, not enlarged 

 upon the sides. The scutellurn offers two yellow spots; the post- 

 scute] is in general black, at times bipunctate. 



I do not doubt but that these little males really belong to tin's 

 species, just as one often meets variations among the insects of 

 this group. These males greatly resemble those of the 0. tigris, 

 but they are however larger, and above all, wider and more stubbed 

 in form. Connecticut. New York. Illinois. 





