DESCRIPTION OF THE SPECIES. 251 



generically they cannot be separated ; the systematic position of 

 these two species and of some South American ones, related to 

 them, will be discussed below (see the last observation to the 

 next following species). 



1?. T. obliqua Sat. $$. (Tab. XI, f. 14.)— Flava, thoracis dorso 

 postice atro-bipunctato, abdomine maris utrinque punctis atris in serieia 

 dispositis quatuor, foeminae quinque notato, alse hyalinse, fasciis quatuor 

 obliquis flavis et fusco-marginatis variegata3. 



Yellow, with two deep-black punctiform dots on the posterior end of the 

 thoracic dorsum, and on each side of the abdomen with rows of four 

 similar dots in the male, and of five in the female ; wings hyaline, with 

 four oblique, yellow crossbands, bordered with brown. Long. corp. 

 0.12—0.14; long. al. 0.13—0.14. 



Stn. Trypeta obliqua Say, Journ. Acad. Phil., VI, p. 186, 3. 

 Trypeta obliqua Loew, Monogr., I, p. 99. 



Say's description, with the additions given by Baron Osten- 

 Sacken in these Monographs, Yol. I, p. 100, is sufficient for the 

 identification of this pretty species. I would only add that in all 

 the specimens examined by me, the males had four, the females 

 five black dots on each side of the abdomen, and that all the 

 specimens showed three deep black dots on the posterior part of 

 the pleuras ; one immediately above the middle coxae, the second 

 above the hind ones, the third crescent-shaped, surrounding the 

 basis of the stem of the halteres. Ovipositor about as long as 

 the last two abdominal segments taken together, of the same 

 coloring as the abdomen, very little infuscated at the end. 



Hob. Indiana (Say) ; Pennsylvania (Osten-Sacken ; on Ver- 

 nonia in August) ; Texas (Belfrage). 



Observation 1. — I am in doubt whether Trypeta obliqua also 

 occurs in Brazil. The specimens generally labelled with this name 

 in the collections, seem to belong to a different, although closely 

 resembling species. They are usually somewhat larger than the 

 North American specimens of T. obliqua Say ; the pile on the 

 whole body as well as the bristles on the third vein are somewhat 

 longer ; moreover, I notice on the sides of the abdomen of the 

 male only two, of the female only three black dots ; not fully 

 colored specimens do not show any trace of the three black spots 

 on the posterior part of the pleurae, as they occur in T. obliqua; 

 better colored specimens have a trace of the two posterior spots 



