170 I1YMEN0PTERA OF AMERICA. [PART I. 



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

 narrow border of the first 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 having more punctures, its antennae mere colored, 

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

 jicxtris by its mctathoracic 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 

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

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

 carefully. 



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

 (10 9,5S.) 



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. 



I possess a very small individual, <j? (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 scuteilum offers two yellow spots; the post- 

 scutel is in general black, at times bipunctate. 



I do not doubt but that these little males really belong to this 

 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. 



