Packard.] INJECTS OF THE POND AND STREAM. 159 
the Notonecta to keep its keel smooth, and it may often be 
seen brushing its back with its hind legs, or where they will 
not suffice, using the middle and front legs for this purpose. 
It lays its long, cylindrical eggs on the stems and leaves of 
plants. The young hatch in about fifteen days, appearing 
in spring. They differ from their parent chiefly in wanting 
wings. 
Corixa is in its form more like the slow moving punt, 
being rounded nearly alike at both ends. The head is still 
more bent and prolonged beneath, partly overlapping the 
thorax. Its beak is minute and hidden from sight. 
So much for the swimming insects, of which we have men¬ 
tioned the principal forms. There are a few of what may be 
called skaters. They move like the Wherryman, or Gerris, 
on the surface of the water, their feet being so constructed 
as to enable them to run upon the surface without wetting 
them. The middle pair of feet are longer than the hinder, 
and they mostly perform the work of skating, being covered 
with fine hairs which repel the water; and thus the insect 
skims over the surface with great rapidity, making very 
short twists and turns like a practised skater. The under 
side of the body is covered with short hairs like plush, form¬ 
ing a repellent surface to the water. 
The fore limbs are much shorter and used at times in re¬ 
taining their prey. Some of these Wherrymen will be found 
minus the hind wings, and are condemned to a life of com¬ 
parative seclusion ; though it is said that the winged indi¬ 
viduals seldom take flight. 
Far out in mid ocean in the tropics are found the oceanic 
water-skaters, the Hylobates. Their fore legs are short, 
outstretched, with thickened thighs. They are also wing¬ 
less, the wing-covers alone being present. Thejr course over 
the surface of the ocean in large swarms, and are seen from 
vessels many hundred miles from land. They are the true 
“toilers of the sea” among insects. 
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