BAKER : HYDROBIUS FUSCIPES. 329 
of the elytra above the surface of the water, slightly opening them 
until the air-supply is renewed, then closing them, thus imprisoning 
the air; but this beetle utilises the hairs on the under surface of its 
body, by their aid entangling a large bubble of air, almost continuous 
from the head to the anal segment, and from which the spiracles are 
supplied. This huge bubble naturally makes the ventral surface lighter 
than the dorsal, and consequently brings the former uppermost. 
On the first approach of winter they bury themselves in the 
mud at the sides of the ponds or streams which they inhabit, and 
with rare exceptions, do not make their appearance again until 
the spring, unlike their carnivorous companions, which may be seen 
disporting themselves throughout the winter on any bright clear day, 
even when the surface of the water is covered by a coat of ice. 
About the middle of March they emerge from their winter 
quarters, and about the second week in April the eggs are first 
lai These are long and cyclindrical, being about 14 mm. in 
length by about 4mm. in diameter. They are enclosed in silken 
Fig. 2. Fig. 3 
Egg Cocoon on blade of grass. x6. Cocoon cut open, with the eggs in situ. 
cocoons (Fig. 2), from nine to thirteen in each cocoon, and not 
placed in any regular way, but simply lying loose (Fig. 3). The 
cocoon itself is attached to the leaves of water-plants or to the 
blades of grass which hang into the water, and being partly filled 
with air floats on the surface of the water if, as often happens from 
one cause or another, it becomes detached. It is formed of closely 
Nov. 1894. s 
