64 S. W. WILLISTON, M. D. 



more recnniBent behind ; the first and second segments on the sides with black 

 bristles- Hypopygium of considerable size, thickly covered above v>rith silvery- 

 white pile. Legs red, the femora and sometimes the tibise with longitudinal 

 black spots, clothed with yellowish hair and black bristles ; hair on the front 

 tarsi deeper yellow, more abundant, on the middle and hind tarsi prevailing 

 black. Wings tinged with pale brownish. 



Bah. — New England, Middle States. 



Numerous specimens from New England, Pennsylvania, etc. The 

 species is nearest allied to cdhifacies^ but the hair is more yellow, the 

 body is less slender, the hypopygium is larger, and the legs are lighter 

 colored. I should be very much inclined to identify this species with 

 Wiedemann's Asilus qitadratns, were it not that Schiner was acquainted 

 with the type of that species, and would hardly have redescribed it under 

 the name of PhUadelphicus were they the same. 



EKAX. 



Macquart, Dipt. Exot. i, 2, 107; 1838. 



Males. 



1. — Costa distinctly thickened and dilat«d beyond the tip of the auxiliary vein. 2. 



Costa not distinctly thickened, etc (slightly thickened in Bastardv) o. 



2. — Hind tibiie on outer third angulated and fringed tagax. 



Hind tibiae simple; dorsum of thorax more or less mane-like 3» 



3. — Hypopygium large, costa considerably thickened; scutellum with long black 



hair and without distinct macrochsetse jubatus. 



Hypopygium of moderate size; scutellum with macrochsetse 4. 



4. — Third, fourth and fifth abdominal segments with long silvery-white pile. 



costalis. 



Third-fifth segments without such pile lafriiiiciiliis. 



5. — Abdomen with long silvery-white pile, parted in the middle and directed 



outward 6. 



Abdomen without such pile 8. 



6. — Three sub-marginal cells auoinaliis. 



Two sub-marginal cells 7. 



7. — Hypopygium elongate; legs black staniineiis. 



Tibiffi yellowish red dubius. 



8. — Hypopygium unusually small ; dorsum of thorax only gently convex longi- 

 tudinally lateralis. 



Hypopygium not unusually small 9. 



9. — Abdomen black, black pilose, the last two segments silvery ; mystax straw- 

 yellow aestnans. 



Abdomen more or less light pilose and pollinose 10. 



10. — Second sub-marginal cell more than half of the length of the first, varipes. 



Second sub-marginal cell not half the length of the first 11. 



11. — Abdomen nearly uniformly grayish pollinose..... leilCOCOinus. 



Abdomen conspicuously black 12. 



12. — The last two segments silvery ftirax. 



The last three segments silvery Bastardii. 



