OSTEN SACKEN ON WESTEEN DIPTEEA. 257 



I have only a single specimen, which, from the breadth of the front, 

 I judge to be a female. 



Head transverse, inserted as in Bomhylius, a little lower than the thorax; 

 as broad as the latter in its broadest part (even a little broader, if the fur 

 be removed) ; the interval between the eyes, in the female, broad, very 

 little narrower on the vertex than near the mouth 5 three large ocelli 

 on a flat protuberance ; eyes reniform ; mouth oval, rather large 5 epi" 

 stoma moderately projecting in the profile in front of the eyes ', cheeks 

 not projecting and head not descending below the eyes; occiput but 

 little swollen, densely clothed with down. 



Proboscis long, three-quarters of the length of the body, and stouter 

 than in a Bombylius of equal size ; palpi elongated, second joint short. 



Antennm approximated at base ; first joint elongated, cylindrical ; 

 second not much longer than broad ; the third one-third longer than 

 the two first taken together, narrow, linear on its first half, gradually ta- 

 pering on the second, truncate at the tip, upon which is inserted a short 

 2-jointed style. I do not perceive any terminal bristle in my speci- 

 men. The whole length of the antenna is about equal to the distance 

 between the ocelli and the mouth. 



Thorax rather long, square, with nearly parallel sides, moderately 

 convex, densely clothed with short erect pile above and with longer 

 hairs on the pleurae ; scutellum comparatively larger than in Bombylius. 

 almost semicircular, moderately convex. 



Abdomen short, much smaller in bulk than the thorax, turned down 

 at the end, unevenly clothed with long pile arranged in semi-erect rows 

 and tufts, which begin at the posterior end of the second segment ; 

 venter hollow. 



Legs like those of Bombylius, only the hind pair comparatively longer: 

 pulvilli much shorter than the ungues. 



Wings and venation as in Bombylius ; the contact of the second sub- 

 marginal cell with the first posterior is very short, almost punctiform ; 

 the same is the case with the second posterior and the discal cell ; small 

 cross-vein about the mjddle of the discal. 



Comastes, in Greek, means a reveler. (I am aware of the existence of 

 Comaster Agassiz, EcMnod., but both the' termination and the derivation 

 of that word are different.) 



CoMASTES ROBUSTUS u. sp., ?. — Grouud-color of the head grayish- 

 white, yellowish round the mouth, densely clothed with pale yellowish- 

 white pile, more yellow on the front; a tuft of black pile on the ocellar 

 tubercle. Antennae black; first joint grayish-pruinose. Palpi reddish, sec- 

 ond joint brownish. Proboscis black. The dense pile on the vertex is 

 yellowish above, whitish below. The grayish-black ground-color of the 

 thorax is almost concealed on the dorsum by a dense, short, erect cloth- 

 ing of fulvous pile; on the pleurre, a tuft of whitish-yellow hair; that 

 on the chest almost white. Scutellum reddish, with fulvous pile and 

 some black bristles along the edge. Abdomen blackish- gray ; second 



