COLEOPTERA. 477 
The Gyrinide, which come very near to the Dytiscide, like 
water which is clear and a little agitated. They are small 
black insects, living in troops, and which swim with rapidity, 
describing incessantly capricious circles, which has gained for them 
the name of “‘ Whirligigs.”” They are remarkable for the disposi- 
tion of their eyes, which are double; so that the Gyrinide 
seem to have four eyes. The lower ones look into the water and 
watch for the prey or the fish that advances as an enemy ; whilst 
the upper eyes look upwards towards the air, and warn the insect 
of the approach of enemies from above. ‘To escape from fish, the 
Gyrinus jumps out of the water, and also makes use of its wings ; 
to escape from birds it dives rapidly. This activity, and this 
double sight, make the capture of the Gyrini a task of great 
difficulty. They must be surprised with a net. At the moment 
of being seized, they emit a milky and fetid liquid. 
The females lay their eggs end to end, on the leaves of aquatic 
plants. The larve are long and narrow, and of a dirty white. 

Fig. 493.—Gyrinus natator. Fig. 494.— Larva of Gyrinus natator. 
They come out of the water at the end of the summer, and form 
for themselves a cocoon on the plants bordering the banks. After 
a month, the perfect insect is hatched, and plunges into the water. 
The Gyrinus striatus (Fig. 495) is found in the waters of Southern 
Europe. 
All these species are of small size, and do not exceed a fifth of 
an inch in length; but in the tropics we find Gyrini two-thirds of 
an inch long. One of these species, distinctus, exists in the little 
lake of Solazies, in Reunion Island, noted for its mineral waters. 
The patients amuse themselves by fishing for this insect, with a 
