DIPTERA OF MINNESOTA. 



35 



In many cases Washington authorities give us only the generic 

 names of specimens sent to them for identification ; this is especially 

 true of Chiroitoinidac and Tipitlidac. 



PSYCHODIDAE. 



Extremely small, fragile moth-like flies, well covered with 

 "hair," whose larvae are found in water, decaying vegetable matter, 

 and even sometimes in cow dung. They are frequently found on 

 the lower surface of leaves and upon windows, and especially in 

 shady places. The different species are hardly one sixth of an inch 

 in length. While they are fairly active on foot, their flight is 



Fig. 18. Wing of moth-like fly, much en- 

 larged. After Comstock. 



not strong. ( )nly four genera are in North America — Psychoda, 

 Pcrico)na, Sycorax and Trichoiiiyia. the most common species, /'. alfcr- 

 iiata. Say, occurring pretty generally over the United States. A few 

 specimens of this species are in our collection. The accompanying 

 drawing, Fig. i8a, represents this fly enlarged. 



Fig. ISa. Psychoda 

 ulternata, enlarged 

 about 8 times. (Orig- 

 inal.) 



Psychoda altcrnata, Say, and a TricJwmyia, sp., occur here. 



