270 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



the first in length, or a little shorter, flattened, somewhat lanceolate, 

 attenuated at the end; terminal style none (in E. marginatus 9, the 

 antennae are a little longer than the head, and the first joint is dis- 

 tinctly longer than the third). 



Thorax but little convex; its dorsum, in U. fumstus, luctifer^Jiar- 

 risii, and muricatus, of which I have only male specimens, is beset with 

 minute, rigid, sharp, conical points, arranged in irregular rows. As JE. 

 marginatus and magnus^ of which I have only females, do not have these 

 points, it seems very probable that this is a sexual character. 



Scutellum comparatively large, almost semicircular, convex, cushion- 

 shaped. 



Abdomen cylindrical, long and slender, by one-half longer than head 

 and thorax taken together; in the male, eight segments, the genitals 

 forming the ninth ; in the females of B. margmatiis and magnus^ I count 

 only seven segments besides that bearing the genitals. 



Legs long and slender, beset with sparse spinules along the tibiae; hind 

 legs by far the longest ; pulvilli distinct, rather broad ; ungues curved, 

 broad at base. In my female specimens, I perceive a few stiff spine-like 

 bristles on the under side of the hind femora, two in E. marginatus; four 

 or five in E. magnus. I do not see anything like it in the males. 



Wings but little shorter than the body, rather narrow, attenuated at 

 the base ; alula small, very narrow. In E. muricatus, the wings are 

 broader. 



Venation. — Two submarginal and four posterior cells; first posterior 

 broadly open; upper branch of third vein gently S-shaped, inserted about 

 the middle of the section of that vein beyond the small cross- vein. The lat- 

 ter corresponds to the middle of the discal cell. Praefurca less than half 

 as long as the distance between the bifurcation and the small cross- vein; 

 second vein gently arcuated on its latter half, reaching the margin with- 

 out forming any sinus ; thus the marginal cell is not expanded at its 

 end. The proximal end of the third posterior cell is opposite the small 

 cross- vein ; anal cell open (Macquart's figure, Dipt. Exot., ii, 1, tab. 11, 

 f. 1, gives a tolerably correct idea of the venation, except that the anal 

 cell IS represented as being closed ; the upper branch of the thiid vein 

 in E. magnus and muricatiis is nearly as bisinuate as represented, but- 

 it is less so in the other species). The costal margin in the male sex is 

 beset with minute blunt points, as in Ploas ; they are almost obsolete in 

 some species {E.funestus) ; very distinct in others {E. muricatus). 



In the following table I include Macquart's E. niger from the data in 

 his description : 

 , Wings infuscated, but anal angle (including at least the second basal, 

 anal, and axillary cells) hyaline : 

 Small species (7-8™°^ long) : 



1. funestus ( i ). — White Mountains, N. H. 

 Large species (12-14™'^ long) : 



Prevailing pubescence black : 



5. magnus ( 2 ). — Vancouver Island. 



