968 FAMILY XXXI. — GERRID.E. 



pronotum, and covered with a short, dense water-proof velvety 

 pile; head shorter than pro- and mesonota united, subconical, 

 inserted in thorax to eyes ; ocelli present, but usually very 

 small and obscure; eyes large, rounded, prominent; antenna? 

 short, rather stout, 4-jointed, inserted on sides of head usually 

 some distance in front of eyes; beak stout, 4-jointed, joints 1 

 and 2 very short ; scutellum and elytra usually absent, the lat- 

 ter, when present, without distinct clavus or membrane and 

 usually reaching nearly to tip of abdomen ; tarsi 2-jointed ; legs 

 very long and slender, femora, coxae and tarsal claws as de- 

 scribed in family key and under superfamily heading. 



Our more common members of this family live upon, not in 

 the pools of quiet waters of streams and ponds. They glide 

 gracefully over these pools borne up by the surface film of the 

 water which, though invisible to human eye, everywhere covers 

 it like a membrane stretched equally in all directions. The 

 wherrymen find this film a pavement well suited for their airy 

 feet, as they skate merrily to and fro in search of living prey. 

 When disturbed they often move so swiftly that they seem but 

 darting lines as they circle round and round each other in a 

 mystic dance. The under parts of the insect are densely 

 covered with fine hairs which form a perfect water-proof vest- 

 ment. The body is held just above the water by the six legs, 

 each of which rests in a little saucer-shaped depression of the 

 water-film. The hind legs, 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 out- 

 line. The middle legs are longer than the others and the por- 

 tion 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 cer- 

 tain angle, they are deflected by the disks, and the resting 

 wherryman forms a most peculiar shadow. When in motion 

 this is rendered more unique by the quick movement of the 

 long propelling legs. 



The adults hibernate beneath cover along the banks of 

 streams and ponds, often at some distance from the water, but 



