Vol. XI] CURRAN— REVISION OF THE PIPIZA GROUP 347 



J. R. Malloch for the privilege of examining the para- 

 type of Cnemodon trochanterata, and to Dr. Aldrich for 

 several suggestions. To the late Doctor Williston I owe 

 much for the determination of specimens, and for sug- 

 gestions regarding several of the new species. To Mr. 

 E. P. Van Duzee I am indebted for a critical reading of 

 the manuscript. 



The disposition of the type specimens of the new 

 species is given following each description. 



Key to the Genera 



1. Face considerably broader at the oral margin than at the antennae. 



(If doubtful, compare Heringia) Pipiza 



Face but little or not at all broader at the oral margin than at the 



antennae 2 



2. Arista microscopically bare; eyes often with a horizontal bare 



stripe Pipizella^ 



Arista microscopically pilose to the end; eyes always evenly pilose. ... 3 



3. Venter of fourth segment in the male only half as long as its 



dorsum; middle tibiae in female slender; third antennal joint in 

 female elongate Heringia 1 



Venter of fourth segment three-fourths as long as its dorsum; 

 middle tibiae in female rounded in front, in male produced an- 

 teriorly; hind trochanters in male usually with long process 



Cnemodon 



•In Pipizella and Heringia the middle tibiae are narrow, often somewhat 

 constricted in front; the females of Pipizella have the bare stripe on the 

 eyes more marked, and, where present, this will at once distinguish them; 

 more difficulty may be experienced with Cnemodon until the student 

 becomes familiar with some species, but usually the shorter and more 

 roundish antennae will help to distinguish the females belonging to that 

 genus. 



Genus Pipizella Rondani 



Triglyphus Loew (Part), P. modestus and pubescens. 



Pipiza Williston (Part), Synop. N. Am. Syrph., 1886. 



Eyes in both sexes often with a median horizontal 

 bare stripe; third antennal joint more than twice as 

 long as wide, usually three or more times longer; arista 

 microscopically bare or pilose at the immediate base 

 only; species usually much shining, sometimes strongly 

 metallic; last section of fourth longitudinal vein bent or 

 angulated at its middle, usually forming a moderately 

 acute, or almost a right angle, with the third vein. 



(The genus Triglyphus is distinguished from other 

 Pipizini by the abdomen being composed of only three 



