184 



APPLIED ENTOMOLOGY 



Family Gerridae. — These insects, the Water Skaters or Water Striders 

 (Fig. 173) as they are commonly called, are often noticed during the 

 summer, skating over the surface of quiet pools of water. Their bodies 

 are slender in most cases, less than half an inch long, usually black or 

 brown, and their long, slender legs project some distance from the body. 

 A few are shorter and broader bodied. They feed on any small insects 

 they are able to capture and winter 

 either under sticks or stones under 

 water, or in mud near the edge, under 

 leaves and rubbish. A few live on 

 the surface of the ocean in warm 

 climates. They are interesting insects 

 to watch but are of little if any 

 economic importance. 



Family Notonectidae. — The Back- 

 swimmers (Fig. 174) as they are 

 termed, live in fresh water. They 



Fig. 173. Fig. 174. 



Fig. 173. — Water Skater {Gerris conformis Uhl.) about natural size. {Original.) 

 Fig. 174. — Notonectids and Corixid: A, Notonectid at the surface of the water 



showing under surface; A', swimming showing upper surface; B, Corixid swimming. 



Somewhat enlarged. {From Linville and Kelly, Text-book in General Zoology.) 



are small, rarely more than half an inch in length and generally black 

 and cream-colored. The back has sloping sides something like the 

 bottom of a })oat and they swim on their backs, propelling themselves 

 by their long legs which are fringed with hairs. They occasionally 

 come to the surface for air, a supply of which they carry down with 

 them under their wings and between the fine hairs covering the under 

 side of the body. They are carnivorous, feeding on other small insects 

 but are of little importance. 



Family Corixid ae. — Living in the same places and with similar habits 

 to the Back-swimmers are small, greenish and blackish mottled insects, 

 rather oval in outline with heads somewhat flattened in front, and known 

 as Water-boatmen (Fig. 174jB). They have long, fringed, oar-like legs 

 but do not swim on their backs and in some way are able to reihain under 

 water without coming up for air for a much longer time than the back- 



