8TRATIOMYIDJ& 45 



often elongated. Legs never thickly pilose ; without bristles, 

 the tibiae without spurs (except in some Beridinae); pulvilli and 

 empodia pad-like. The costal vein of the wings does not 

 reach to the tip of the wing ; veins often crowded anteriorly, 

 and those posteriorly weak ; discal cell present ; four or five 

 posterior cells, and one or two submarginal cells present, the 

 anterior branch of the third vein short and often indistinct. 



The family Stratiomyidae is one of considerable size, in- 

 cluding nearly one thousand known species. The flies are 

 invariably flower insects, seldom with any marked powers of 

 flight and never having the habit of hovering in the air. Not 

 a few species are caught in beating nets or on the windows of 

 dwelling houses. Many of the species have in life bright yel- 

 low or green markings. Their eggs are laid on the ground, on 

 plants about water, or perhaps on the surface of the water 

 itself. The larvae are carnivorous, or feed upon decaying veg- 

 etable material. The larvae of Chrysomyia have been found 

 in cow-dung, and under stones ; those of Sargus in the flowing 

 sap of elm trees ; those of Hermetia in privies ; those of Pachy- 

 gaster in decaying wood ; those of Beris in moss ; those of 

 Stratiomyia, Odontomyia, Nemotelus, etc., in water. The lar- 

 vae of Stratiomyia have been found in salt and alkaline water. 

 The body is smooth and flattened, the last segment often pro- 

 longed into an elongated breathing tube and with a terminal 

 transverse cleft. The pupae are inactive, remaining within 

 the larval skin, the pupal skin remaining within, or partially 

 within, the larval skin when' the fly escapes through a longi- 

 tudinal rent. 



TABLE OF GENERA. 



1. Abdomen with seven visible segments. . . . . ".. BERIDINAE. 

 Abdomen with five or six visible segments. . . ' . . 2 



2. Three posterior veins,* all arising from the diseal cell. PACHTGASTRIN^:. 

 Four posterior veins, the anterior ones sometimes rudimentary. . 8 



* By posterior veins isjneant those separating the posterior cells. 



