294 
TRANSFORMA TIONS OF INSECTS. 
female Hydrophilidce — the extremity of whose abdomen is fur- 
nished with two cylindrical appendages or thread drawers — set 
to work immediately after they have laid their eggs to enclose 
them in a cocoon, the silken threads of which afford them a safe 
and secure protection against the multitudes of other insects that 
are always on the look-out for animal matters. The eggs float 
in this cocoon until they are hatched. The larvae are generally 
oblong, and have rather a projecting head without any neck-like 
constriction. They have large mandibles, which are curved near 
the extremity, and are often dentated. They have coriaceous 
plates upon the body segments, and the last segment of the 
abdomen is very small ; their legs are rather long, and the tarsi 
are usually unguiculate. Although they have not the agility of 
the larvae of Dytiscus (the true water beetle), they are very active, 
and care principally for a vegetable diet, but, nevertheless, they 
are sometimes carnivorous and very voracious, and eat the fry of 
fishes and small mollusca. Being almost amphibious they may be 
seen to leave the water and to crawl with some difficulty amongst 
the grass on the sides of ponds and streams. When about to 
undergo the first metamorphosis they bury themselves in the 
earth or in the mud, where they make a cavity, daubing over 
its inside with their saliva ; when the cavity is finished they 
become nymphs. Although there are not many species in the 
family, there are some very characteristic forms amongst them. 
The genus Hydrophilus contains large insects of an oval 
form, having antennae with nine joints, the last four ‘forming 
the club. These beetles have two long, very solid, and sharp- 
pointed spurs, which, when they are laid hold of incautiously, 
can inflict a sharp wound. They are found in many parts of the 
world, but only one kind, Hydrophilus piceus , commonly called 
Hydrous piceus , inhabits Europe, and it is the largest. It is 
a well-known beetle, and is an inch and a half in length, 
being of an olive-black colour. It swims with great facility, on 
account of its hind legs being flattened, ciliated, and able to be 
used as oars. It is an interesting inhabitant of fresh-water 
aquaria. The manner in which it comes to the surface of the 
water, and the way in which it breathes, when it does so, always 
excite interest. The Hydrophilus , which is a big beetle, could 
