THE CANADIAN ENTOMOLOGIST. 



mens frequently furnish grounds for much more decided opinions than a 

 richer material will sustain. I describe in the present paper five species 

 that present characters sufficiently decisive to render their recognition not 

 doubtful ; other species I forbear to name till my material is richer. It 

 will be seen that I make little use of the structure of the arista, a character 

 that has been relied upon much in the European species ; but I am satis- 

 fied that it is a variable one in individuals of the same species, and is, 

 moreover, distinctly sexual. There is a distinct variation in different 

 species in the position of the anterior cross-vein, as regards the termination 

 of the auxiliary ; of how much value the character is I am not yet decided. 



Generic characters. — Moderately large species, not very bristly. Head 

 very large, inflated ; front very broad, only a little narrower in the male, 

 with numerous, not very strong bristles ; face in profile nearly perpendicu- 

 lar, the epistoma but slightly projecting ; the oral margin with a row of 

 bristles, not ascending on the edges of the median facial depression. 

 Cheeks broad ; bare, or with short bristles. Antennae elongate ; third 

 joint two or three times as long as the second in the female, from four to 

 eight times in the male ; arista stout, composed of three joints, the second 

 and third elongate, and joining each other at an angle, as though broken. 

 Eyes bare. Palpi cylindrical. Scutellum with six strong bristles on its 

 border. Abdomen broad oval or ovate ; first and second segments each 

 with a pair of median posterior bristles and one extreme lateral posterior 

 one ; third segment with a row on the posterior border. No spinule at 

 tip of auxiliary vein ; fourth vein obtusely angulated, without stump of 

 vein, terminating in the costa a considerable distance before the tip ; pos- 

 terior cross-vein much nearer the angle than to the anterior cross -vein. 



Head yellow, except the occiput, palpi yellow ; thorax black, margins 

 of dorsum and scutellum often yellowish ; legs black. Larvte, so far as 

 known, parasitic on hymenoptera and lepidoptera. 



Table of Species. 



I. — Abdomen wholly black, or at most only somewhat reddish on the 

 sides of base ; claws and pulvilli of male small. . frontosa Say. 



Abdomen largely or wholly red or yellow.. 2 



2. — Face and antenna golden yellow ; claws of male small. . senilis, n. sp. 



Face and antennae not golden yellow 3 



3. — Sides of face, pleurae and femora with yellow hair ; claws and pulvilli 

 of male small porca, n sp. 



