102 



APPLIED ENTOMOLOGY 



eyes are so divided that one part of each is directed upward and the other down- 

 ward (Fig. 85). They feed on small insects which come within their reach. The 

 larvae, living in the water, breathe by abdominal tracheal gills, and are also 

 carnivorous. The group does not include many species, but their habit of 

 swimming in companies, and their peculiar " gyrating" over the surface attracts 

 attention, nearly everybody having noticed them on this account. 



Family Hydrophilidae (Water-scavenger beetles). The water-scavenger 

 beetles occur in the same types of stream and pond as the carnivorous diving 

 beetles, which they greatly resemble (Fig. 86). The outline, however, is usually 

 a little more elongately oval; the antennae are club-shaped, and in addition to 

 other structural differences, they obtain air by raising the head slightly above 



FIG. 85. FIG. 86. FIG. 87. 



FIG. 85. Gyrinicl or Whirligig Beetle (Dineutes), natural size. (Original.) 

 FIG. 86. Water-scavenger Beetle (Hydrous triangularis Say), natural size. (Original.) 

 FIG. 87. Rove-beetle (Staphylinus vulpinus Nordm.), slightly enlarged. (Original.) 



the surface and collecting a film of it over the under surface of the body, where 

 it is retained by a close coating (pubescence) of fine hairs. They feed on decay- 

 ing animal and plant material for the most part, though sometimes taking to 

 living plants and insects. Some species may be about two inches in length. 

 They are of little economic importance. 



Family Staphylinidae (Rove-beetles). This large family in some regards is 

 suggestive of the fire flies as the body of the insect in this group is not as hard 

 and firm as in most beetles and seven or eight abdominal segments are present 

 (Fig. 87). In other ways, however, it differs greatly from the Lampyrids, the 

 body being slender for its length, and the elytra short, not nearly covering the 

 top of the abdomen, the segments of which are very movable. The insects run 

 rapidly, often lifting up the end of the abdomen in a menacing way. Most of 

 the thousand or more species found in this country are small, the larger kinds 

 seldom being more than an inch long. They are land forms, feeding on decay- 

 ing vegetable and animal materials near which, or under stones and wood, 

 they are found. They must be considered as beneficial insects, acting as scav- 

 engers. 



