noLiCHoronnm 77 



some cases the males have small snow-white spots in the tip 

 of the wing. Anal cell always very short. 



This family perhaps surpasses any other natural group of 

 animals in the variety of sexual ornaments possessed by the 

 males. These are paraded before the females, as are similar 

 ornaments in the peacock and turkey-cock. See " Courtship 

 Among the Flies ", American Naturalist, Jan. '94, p. 35. 

 They may occur in almost any external portion of the body. 

 In a careful examination of a large number of species, I have 

 never found any two in which they are identical. I am ac- 

 quainted with at least fifty different forms of tarsal modifica- 

 tion alone, every one of which is distinctive of its species. 

 Nevertheless some species seem to offer no noticeable sexual 

 differences beyond the presence of the hypopygium in the 

 male ; even this is in some cases but little visible. 



In adult life all are predaceous, capturing chiefly the 

 minuter soft bodied flies, which they enclose within their soft 

 labella, while extracting the juices ; the larvae are, as far as 

 known, feeders on decaying vegetation. 



The following table is designed solely to enable beginners 

 to determine the genera of their specimens : it does not, there- 

 fore indicate anything about the natural relations of the gen- 

 era to each other. It is based on male specimens only, since 

 otherwise it must have included many obscure and difficult 

 characters. 



TABLE OF GENERA. 



1. Fourth longitudinal vein with a widely divergent fork on the front side; 



or if not, the head wider than the thorax, face wide, and the front 

 deeply excavated (Psilopinae). ....... 2 



Fourth vein simple or merely broken , front not excavated. . . 5 



2. Fourth longitudinal vein not forked. . . AproRTiirs Aldrich. 

 Fourtli longitudinal vein forked. ....... 3 



3. Tegular cilia black, third longitudinal vein curved genth" back at tip, 



scutellum with four large bristles. . . . PSILOPUS Meigen. 

 Tegular cilia pale, third vein distinctly curved forward at the tip, scu- 

 tellum with two large and usually two small bristles. . . 4 



