128 NORTH AMERICAN DIPTERA 



Family Bibionidse — The March Flies 



Slender flies of small to medium size, ranging from four to twelve 

 millimeters in length. 



Head usually somewhat flattened; eyes of the males approximate 

 or contiguous, of the females, broadly separated; face rather short, 

 sometimes elongate in Dilophus; eyes round; ocelli large. Antennae 

 composed of eight to twelve segments, cylindrical or somewhat flattened, 

 the segments rather closely united. Proboscis short, with thickened, 

 hairy labellae; palpi with two to five segments, usually short, some- 

 times long. Thorax without transverse suture; scutellum hemicircular. 

 Abdomen composed of seven to nine segments, more or less flattened, 

 the male genitalia rather small. Legs moderately long, the anterior 

 femora usually thickened, sometimes greatly swollen, the other femora 

 usually somewhat swollen; anterior tibias usually modified, often greatly 

 swollen in Bihio; legs slender in Plecia. Pulvilli and usually the 

 empodium distinct. Wings large, the anterior veins stout, the others 

 usually considerably weaker; costa ending at or before the wing-tip; 

 second vein present or absent; fourth vein furcate; basal cells com- 

 plete; anal cell rarely closed; posterior crossvein absent. 



The larvffi feed upon decaying vegetable matter, especially upon 

 the roots of grass, and pupation takes place in the soil. The adults are 

 frequently very common and may be found almost anywhere in the 

 open. The name "March Flies" has been given the family in this 

 country because of the frequent occurrence of Bihio aJhipennis Say in 

 large numbers during this month. "Harlequin Flies" is used in Eng- 

 land, while "March Flies" is applied to other flies in Australia. The 

 family has been review^ed by MacAtee*. 



KEY TO GENERA 



1. Third vein furcate (6, 7) 2 



Third vein not furcate (5) 5 



2. Fourth and fifth veins forked 3 



These veins not forked Eupeitenus Macquart 



3. Antennae with not more than 12 segments 4 



Antennae with 16 segments (7) fCramptonomyia Alexander 



* 1921. Proc. U. S. N. M. Ix, Art. 11. 



t For a discussion of tlie position of this genus and its allies see Alexander, 1931, Bull. 

 Brooklyn Ent. Soc. xxvi, pp. 7-11. 



