COLEOPTERA . 
527 
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 Gyrimis (Gy-ri'nus) the scutellum is 
visible; of this genus we have twenty-seven species. 
Family HYDROPHILID^ (Hyd-ro-phil'i-da?). 
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 antenna? 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 
