334 The Ohio Naturalist. [Vol. XIV, No. 8, 



Microdon coarctatus Loew. A small bright green species 

 with many of the wing veins margined with dark brown. Three 

 specimens from Louisiana. 



Microdon flavitibia Walker. Thorax and abdomen purplish 

 black. Wings fumose. Of the same form and size as bidens. Six 

 specimens from Bartica, British Guiana. 



Microdon ruiiventris Rondani. Face, front and thorax 

 shining green clothed with golden pile; antennae brown; abdomen 

 reddish yellow with the exception of a triangular green spot near 

 the scutcllum. Legs pale, wings nearly hyaline. Length 11 

 mm. One specimen from Bartica, British Guiana. 



MixoGASTEn Macquart. 



Fiv^e American species have been described in this genus. 

 Some of them might well be placed in Microdon were it not for 

 the discinctly clavate abdomen but others do not show such close 

 relationshi]j with that genus. M. breviventris Kahl is the only 

 species that has been taken as far north as the LTnited States. 

 An additional species was taken at Los Amatcs, Guatemala, and is 

 here described as new. The following key for the separation of 

 the known species has been compiled in large measure from 

 descriptions and figures that have appeared in various publications. 



1. Thorax with a middorsal yellow stripe, conopsoides Macq. 

 Thorax not with a middor.sal yellow stripe. 2. 



2. The third longitudinal vein emits a stump into the first posterior 



cell. 3. 

 The third longitudinal vein does not emit a stump into the first 

 posterior cell. 4. 



3. Wing clear hyaline, legs brown, claripennis n. sp. 



Base of marginal cell and a cloud along the third vein brown, 

 bases of all the tibia; light yellow, hellulu Will. 



4. The vein closing the distal end of the first ])r)sterior cell ahuost 



straight, breviventris Kahl. 

 The vein clo.sing the distal end of the first i)Osterior cell distinctly 

 angulated. 5. 



5. Face extraonlinarily arcuate, diniidiald G. Tos. 

 Face normal, mexicana Macq. 



Mixogaster claripennis n. s]). Lcngtli about 10 mm., l)ody 

 black with yellow bands, legs generally brownish. Face yellow 

 on each side and black at middle, clothed with yellow ajjpressed 

 hairs, cheeks black; front largely shining black narrowed near 

 lower third where there is a transverse space clothed with short 

 yellow hairs, vertex tumid, also a prominence just above base 

 of antenna?. Antennre long, first segment long and slender, 

 second segment short, third segment thickened and about as long 

 as the first, whole antenna black except the extreme base of first 

 segment which is yellow. Thorax black in ground color, humerus 

 with a very small pale s]jot, suture with a ver>' narrow band of 

 yellow pile. Scutcllum golden pilose. Wings clear hyaline. 



