MOVEMENTS OF AQUATIC INSECTS. 207 



hind ligs, from the knee down, rest on the 

 water, and the indentations formed by them 

 are long oval in form, while those made by the 

 front legs are circular in outline. The middle 

 legs are longer than the others and the portion 

 of them touching the water is smaller. The 

 insect uses only these middle legs in propelling 

 the body, moving them in a quick, forward 

 stroke like a pair of oars. It thus glides or 

 skates on the front and hind legs, the disks 

 which they form seemingly traveling with the 

 insect. In early morn and late afternoon, 

 when the rays of the sun strike the water at a 

 certain angle, they are deflected by the disks, 

 and the resting wherryman forms a most pecu- 

 liar shadow. When in motion this is rendered 

 more unique by the quick movement of the 

 long propelling legs. 



Of water beetles, a score or more of kinds in- 

 habit the depths of the pools. Most of them are 

 both predaceous and voracious, feeding not only 

 upon other insects, but even small fish. During 

 the mating season, many of them leave the 

 water at night and are often attracted by elec- 



