DIPTERA OF MINNESOTA. 



69 



whitish, milky wings, contrasting with its black body. They all 

 fly heavily, and are quite likely to be found among grass and other 

 vegetation close to the ground. The sexual differences in coloration 

 are striking, and oftentimes so marked as to lead one to think that he 

 is looking at a different species. In this connection we might speak 

 of another striking structural difference between males and females 

 of many soecies. viz. : not only are the eyes of the males contiguous, 

 but each eye is divided into a large upper portion and a small lower 

 portion. The larvae or maggots feed upon vegetable matter, some 



Fig. 57. Bibio albipennis, female. 

 Original. 



Fig. 58. Bibio albipennis, male. 

 Original. 



forms being particularly fond of roots of grasses. While they can 

 hardly be regarded as pests, one species, Dilophus febrilis, the so- 

 called Fever Fly, very common in Great Britain, causes serious injury 

 to hops by feeding on the roots of the vines. 



There are three hundred or more described species of the family, 

 and they have a wide range, from Scandinavia to the tropics. Their 

 range in time, or geological range, is not extensive, though they are 

 more abundant in fossil form than any other insect. The writer has 

 captured B. albipennis, Say, very commonly in Minnesota in May and 

 June, and B. pallipes, Say, at Basswood Lake in June. B. variabilis, 



Note. — In a few cases we have found specimens in the collection labeled 

 South Dakota, not represented by species from this state. Since they are with- 

 out doubt also found in Minnesota, though not yet taken here, we have in- 

 cluded them with the Minnesota species; in every case, however, disignating 

 them by the abbreviation, "So. Dak.," placed after the name. 



