• AMERICAN DIPTERA. 199 



style or arista, terminal, except in a few genera, where it is sub-dor- 

 sal. It may be short, stubby, thick, and two-jointed, as the style, or 

 slender and hair like, and several times the length of the antenna, 

 as the arista. In one case {Hilara Johnsoni) the arista is spirally 

 curled. The arista is never plumose. The basal antennal joints 

 may be more or less bristly, but this is not the case with the third 

 joint ; this joint varies greatly in shape, it may be short and stunted, 

 rather large and globose, oval, or lanceolate. The face may be ob 

 literated by the contiguity of the eyes, or may be broad and con- 

 vex, with the clypeus prominent, nearly always bare. On the occi- 

 put the postocular bristles are more or less prominent, as are also the 

 ocellar bristles. 



The thorax is often prominent, larger than the remainder of the 

 body and hunchbacked ; though sometimes more or less flattened 

 dorsally. The humeral angles may be prominent. The dorsum and 

 pleurae are generally covered with glaucous pollen. The arrangement 

 and the size of the bristles and hairs are extremely variable. The 

 margin of the scutellum is provided with from two to very many 

 bristles. 



The abdomen is generally long and slender and more or less cyl- 

 indrical, sometimes broad and flat, consisting of five to seven seg- 

 ments, its hairiness variable. Ovipositor simple, generally small, 

 sometimes projecting as in Leptopeza ; hypopygium prominent, often 

 large and extremely complex, generally reflexed over the abdomen. 

 The ventral spots so characteristic of most dolichopodid genera are 

 conspicuously present in Coloboneura and many Empis. 



Legs of varying structure, often the coxse and femora are elonga 

 ted, often the femora are thickened and provided with spines below ; 

 in Hemerodromia the fVont ones are enlarged, in Platypalpus the 

 middle ones, in Hybos the hind ones, in Pachymeria all, etc. ; the 

 metatarsi of the males of Hilara and some Empis are peculiarly en- 

 larged ; the legs of various species are provided with characteristic 

 ornaments, the femora and tibite of some females being ciliated with 

 scale-like hairs, while of some males they are armed with projecting 

 structures. The arrangement of the bristles is variable, as is the 

 amount of hair present. Pulvilli moderate, empodia small, ungues 

 plain. 



Wings normally parallel with the body, rather large, long, and 

 narrow ; neuration variable. The discal cell may be present or 



TRANS. AM. ENT. SOC, XXVIII. JULY, 1902. 



