Packard.] INSECTS OE THE POND AND STREAM. 157 
and are articulated by an exquisite mechanism to the body. 
They are edged on the inner side with a dense, long fringe 
of exceedingly fine, white hairs, forming, with the flattened 
leg itself, the blade of the oar; and thus by a series of 
rapid strokes the body is propelled onwards. The fore legs 
are short and thick, and in the males modified into a clasp¬ 
ing organ, the three basal joints of the tarsus being broadly 
dilated and consolidated into a large disk, covered with 
“ many minute funnel-shaped suckers, two or three of which 
are much larger than the others.” The Gyrinus is less a 
fig. 125. 
Male and Female Dytiscus. 
diver than a surface swimmer. It is a very sociable insect, 
forming little swimming parties on the surface of the water. 
In the course of its gyrations it manages to pick up a com¬ 
fortable livelihood of small beetles and flies which fall into 
the water. When disturbed it dives to the bottom. Unlike 
the other water beetles it has very large fore legs and re¬ 
markably short middle and hind legs, and flies about in the 
night, at daylight slipping quietly into some pool. On 
being handled it emits a disagreeable, whitish, milky fluid, 
which is probably distasteful to its enemies. All the other 
29 
