Order DIPTERA. 



Families PIPUNCULID^, SYRPHID^, 

 CONOPID^, CESTRID^. 



Tnis volume is devoted to the above four families, the systematic 

 account of which was excluded from tlie volume entitled "Diptera 

 Brachycera, Vol. I," published in 1920. Tliey are, however, 

 referred to in the Introduction to that volume, and are included 

 in the key of families given therein on pp. 6-9. 



Family PIPUNCULID^. 



Head nearly globose, practically all eyes, distinctly broader than 

 thorax, and very loosely though rather closely applied to it, 

 generally considerably puffed out behind. Eyea bare, usually 

 contiguous in S for some distance, occasionally subcontiguous 

 only, facets enlarged ; frons in 5 narrow, front facets enlarged, 

 sometimes very considerably ; three ocelli ; face very narrow and 

 elongate in both sexes. Proboscis very small, concealed, as are 

 the palpi, which are said to be clavate, rarely visible. Antennae 

 3-jointed; first two joints very short ; 3rd more or less elongate, 

 oval or rounded, generally (Pipancidus) broad at base, gradually 

 contracting to a blunt or sharp point; or rounded {VerraUia, 

 Chalarus)- the always long, bare, basally thickened arista placed 

 at the base of the joint. Some small ocellar and vertical bristles 

 in VerraUia and Chalarus, but Pipunculus has no head-bristles. 



!Z7jo»ym; subipiadrate ; bare (i-'/y>M/if«/j(,s) or with small but dis- 

 tinct bristles {VerraUia, Chalarua.) ; scutellum usually bare, rarely 

 slightly pubescent, or with marginal bristles. 



Ahdomen normally cylindrical, longer than thorax, generally 

 more or less curved, 5-segmented in ^ , 6-segmented in $ , usually 

 bare, but sometimes slightly or distinctly pubescent. Genitalia 

 in S Ifirge, conspicuous, affording good specific characters ; * 

 ovipositor in $ bulbous at base, the remainder long, pointed, and 

 curved under the venter. 



Lejs moderate in length and size, bare, except for a few very 

 short bristles beneath some of the femora in certain species ; hind 



* I have not devoted mticli study persoimlly to tlie genitalia, but according 

 to E. T. CresBon, Junr., these organs ivre similar in structure thougli diverse in 

 form, and are apparently variable to some extent in certain .species (see Trans. 

 Amer. Ent. Sue. xxxvi, pj). 27U-1, Dec. I'JIO). 



B 



