DIPTERA. 



479 



disease known as " staggers." When full-grown they pass 

 out through the nostrils and undergo their transformations 

 beneath the surface of the ground. 



Other species infest rabbits, squirrels, deer, and reindeer. 

 One that lives beneath the skin of the neck of rabbits is very 

 common in the South. 



Family MUSCID.E (Mus'ci-dae). 

 The Muscids {Mus'cids). 



The form of the more typical members of this family is 

 well shown by the common House-fly. But the family is a 

 very large one and includes species that differ greatly in 

 form. These differences are so great and so varied that 

 some writers divide the family into nearly thirty families. 

 It seems to us, however, to be better to consider these 

 divisions of subfamily value. The following characters are 

 presented by the family as a whole. 



The antennae (Fig. 586) are three-jointed ; the third seg- 

 ment bears a dorsal bristle. The frontal suture is present 

 (Fig. 587). The proboscis is 

 always present. Vein II of 

 the wings may be present or 

 absent ; vein III is three- 

 branched ; cells Vj and V 3 are 

 wanting ; the branches of vein 

 VII coalesce with the adjacent 

 veins (VII, with V, , and VII a 

 with IX) for nearly their 

 entire length. The pulvilli 

 are present, and the empodia 

 are never pulvilliform. 



As this family includes more than one third of all the 

 known Diptera, it usually happens that a large proportion 

 of the flies in a collection belong to it. It seems necessary, 

 therefore, to indicate some of the principal divisions of the 



Fig. 586. 



Fig. 587. 



