38 NORTH AMERICAN DIPTERA. 



occurs early in tlie spring, in great nTimbers, especially about 

 willows, and in gardens. It is conspicuous for its white wings 

 and black color, and like most other members of the family is 

 slow in its movements, flying heavily. B. fevinrata, a com- 

 mon species, is of a deep red color with black wings. B. trlstis 

 has been observed in large numbers in many Kansas wheat- 

 fields, during the last week of A})ril, apparently without 

 causing damage. 



1. Second basal cell present. ........ 2 



Second basal ceil wanting. ........ 5 



2. Third longitudinal vein furcate. . . . . . . . 3 



Tliird vein not furcate. ......... 4 



3. Pal])! four-jointed ; first antennal joint elongate. Hespkrinus Walker. 

 Palpi five-jointed. Pi.kcia Wiedemann. 



4. Front tibiaj with a stout, s])ine-like process at the tip. Ribio Geoffrey. 

 Front tibite with a terminal coronet of spines. Dilophus Meigen. 



5. Front tibia? ending in a spine-like process. . . Aspistes Meigen. 

 Front tibia? of the usual structure; third vein not furcate; hind meta- 

 tarsi sliorter than tlie remaining joints togetiier. Scatopse (ieoffrev. 



11. SIMULIID^. 



Small flies, from three to six mm. in length, with thick, 

 compressed, short legs. Head hemispherical; face short; 

 eyes round or reniform, holoptic in the male ; no ocelli. 

 Antenuffi scarcely longer than the head, cylindrical, ten- 

 jointed; the two basal joints diiferentiated, the others closely 

 united. Proboscis not elongated, with small, horny hibella ; 

 p;ill)i incurvate, four-jointed; the flrst joint short and the two 

 following of equal length ; the last one longer and more slen- 

 der than the preceding. Thorax ovate, without suture ; the 

 scutellum small. Abdomen cylindrical, composed of seven or 

 eight segments; genitalia concealed; legs strong and not elon- 

 gated; femora broad and flat ; tibia3 without terminal spurs ; 

 first joint of the tarsi longer than the following and usually 



