The Two-winged Flies 



329 



feeding on small aquatic or underground creatures, especially insect larvae 

 and snails or slugs. 



Nearly 200 species of horse-flies are known in North America. The 

 large bluish-black and brownish-black ones, an inch long and with dusty 

 wings expanding for two inches or more, belong to the genera Tabanus and 

 Therioplectes; the smaller ''greenheads" with banded wings and brilliantly 



Fig. 459. — Mouth-parts of a horse-fly, Therioplectes sp. md., mandible; mx., maxilla; 

 mx.l., maxillary lobe; mx.p., maxillary palpus; hyp., hypopharynx; lb., labrum; 

 €p., epipharynx; //., labium; la., iabellum. 



colored eyes and black or brown and yellow bodies mostly belong to the 

 genus Chrysops. Silvius poUinosus is a beautiful small species with a milk- 

 white bloom over its body, and with clear whitish wings with a few small 

 brown spots. 



The soldier-flies, Stratiomyidae, are unfamiliar insects, although as many 

 species of them as of horse-flies occur in this country. Many of the species 

 have bright )-ellow or green markings, and most of them have the abdomen 

 curiously broad and flattened. 

 They are found about flowers, 

 and can readily be classified, 

 after capture, by the unusual 

 character of the venation (see 

 Fig. 460). The eggs are laid 

 on the ground or on leaves in or 

 near water, some of the larva; 

 being terrestrial, while others are 

 aquatic. The food seems to be mostly vegetable, although the lar\a; of some 

 species are believed to be carnivorous. One or two species Hve in salt or 

 brackish water, and Sharp records that some Stratiomyid larva? were found 

 in a hot spring in Wyoming with the water temperature only 20° to 30° F. 

 below boiling. They pup;ite witiiin the last larval skin, which is long and 



Fig. 460. — Diagram of wing of Odonlomyia 

 sp., showing venation. 



