The Two-winged Flies 341 



The abundant house-flies are the most familiar representatives of the 

 largest of all the Dipterous families: largest if the great heterogeneous 

 group of flies called Muscidae is to be looked on as a single family, a point of 

 view taken by some entomologists, but not so if this group is called a 

 superfamily, composed of a large number, about twenty in all, of distinct 

 small families. The group includes, besides the house-flies, the buzzing 

 bluebottles, the disgusting flesh-flies and stable-flies, the parasitic Tachina 

 flies, the pomace-flies, fruit-flies, grass-stem flies, brackish-water flies, and 

 numerous other kinds not familiar enough to have a vernacular name. To 

 get acquainted with some of the more abundant and interesting kinds, and 

 to enable us to classify them to subfamilies (if the whole group is called 

 family), we may scrutinize any fly which our key on page 332 leads us to 

 call a Muscid, in the light of the following key: 



(The first posterior cell is the space between the little cross-vein in the middle of 

 the wing and the outer margin of the wing. See in Fig. 490.) 



Alulets small ACALYPTRATE MUSCID.E. 



Alulets large CALYPTRATE MUSCID.E. 



First posterior cell widely open Subfamily ANTHOMYIUSLE. 



First posterior cell narrowly open or closed (Fig. 490). 



Antennal bristle wholly bare Subfamily TACHININ.E. 



Antennal bristle with some distinct hairs. 



Antennal bristle bare near the tip Subfamily SARCOPHAGIN^E. 



Antennal bristle plumose or pubescent to the tip. 



Back of abdomen bristly, legs unusually long Subfamily DEXIIISLE. 



Back of abdomen not bristly, except sometimes somewhat so near tip. 



Subfamily MusciN^;. 



The Acalyptrate Muscidae include a host of small, mostly unfamiliar, 

 flies, distributed among a score of subfamilies. We shall refer to a few 



FIG. 483. FIG. 484. 



FIG. 483. House-fly, Musca domestica. (After Howard and Marlatt; three times 



natural size.) 

 FIG. 484. Foot of house-fly, showing claws, pulvilli, and clinging hairs. (Greatly 



magnified.) 



of the more interesting kinds in the group after taking up briefly the five 

 subfamilies of larger, more noticeable Calvptrate Muscids. 



