294 TRANSFORMATIONS 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 larvse are generally 

 oblong, and have rather a projecting head without any neck-like 

 constriction. Tliey 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 larvse of Dytisciis (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 HydropJiilus 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, HydropJiilus 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 HydropJiilus, which is a big beetle, could 



