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.h, maxillary lobe; mx.p., maxillary palpus; hyp., hypopharynx; lb., labrum; 
ep., epipharynx; li., labium; la., labellum. 
colored eyes and black or brown and yellow bodies mostly belong to the 
genus Chrysops. Silvius pollinosus 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, Stratiomyidse, are unfamiliar insects, although as many 
species of them as of horse-flies occur in this country. Many of the species 
have bright yellow 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 larvae 
being terrestrial, while others are 
aquatic. The food seems to be mostly vegetable, although the larvae of some 
species are believed to be carnivorous. One or two species live in salt or 
brackish water, and Sharp records that some Stratiomyid larvae were found 
in a hot spring in Wyoming with the water temperature only 20° to 30° F. 
below boiling. They pupate within the last larval skin, which is long and 
Fig. 460. — Diagram of wing of Odontomyia 
sp., showing venation. 
