COLEOPTERA. $ 2 7 



North American species are known. These represent three 

 genera. The genus Gyretus (Gyr'e-tus) is distinguished by 

 having the last ventral segment of the abdomen elongated 

 and conical. It is represented by a single species, G. sinuatus 

 (G. sin-u-a'tus). In the other two genera the last ventral 

 segment is flattened and rounded at the tip. In Dineutus 

 (Di-neu'tus) the scutellum is wanting; there are eight spe- 

 cies of this genus. In Gyrinus (Gy-ri'nus) the scutellum is 

 visible ; of this genus we have twenty-seven species. 



-/_ Family HYDROPHILID^E (Hyd-ro-phiri-dae). 

 The Water-scavenger Beetles. 



The water-scavenger beetles are common in quiet pools, 

 where they may be found swimming through the water, or 

 crawling among the plants growing on the bottom. They 

 can be easily taken by sweeping such plants with a dip-net. 



They are elongated, elliptical, black beetles, resembling 

 the predaceous diving beetles in appearance ; but they are 

 usually more convex, and differ also in having club-shaped 

 antennae and very long palpi. As the antennas are usually 

 concealed beneath the head, it often happens that the inex- 

 perienced student mistakes the long palpi for antennae. 



These beetles are supposed to live chiefly upon decaying 

 vegetation in the water; but a number of species have been 

 known to catch and eat living insects. They breathe by car- 

 rying a film of air on the lower surface of the body. This 

 film gives them a silvery appearance when seen from below. 

 They obtain the air by bringing the head to 

 the surface of the water and projecting the 

 antennae, which they again fold back with a 

 bubble of air when they descend. The female 

 makes a case for her eggs out of a hardened 

 silk-like secretion. Some species deposit as 

 many as a hundred eggs in one of these water- 

 proof packages (Fig. 636). The egg-cases in 

 some instances are fastened beneath the leaves of aquatic 



