310 



NATURAL HISTORY, 



covers ; the anal segments of the body being depressed for the freer passage of the air. They are able 

 to make good use of their wings, leaving the water and flying to distant ponds in fine summer 

 evenings. For defensive purposes, they have the same faculty as the Carabidse of emitting a fetid 

 liquid, but where this has been observed it is not, as in Carabidse, by the anus, but through the 

 interval between the head and the thorax. 



The larva?, more voracious and fiercer in aspect than the adult insects, are hatched from the cylin- 

 drical eggs in early spring and in autumn. They are of similar general form to the larvae of the 

 Carabidse, and differ from the pei'fect insects in their heads, as well as the other parts of their long 

 bodies, being free and mobile. Their mouths are armed with long and sharp sickle-shaped mandibles, 

 well adapted to seize their prey, which consists of the larvae of other insects, even of their own species, 

 fresh-water molluscs, and sometimes young fishes. They quit the water to undergo their transforma- 

 tions, excavating a chamber in the soil, in which they pass into the pupa stage, emerging in due 

 time as adult beetles. 



The family includes two distinct sub-types, which some recent authors are inclined to treat as 

 separate families. In the one (Haliplinai), consisting of species of small, or minute size, some of the 

 essential peculiarities of Dyticidse are wanting, such as the natatory hind legs, which do not differ in 

 form from those of many Carabidse. The posterior haunches, in correlation, are also not enlai-ged in 

 front, although differing from those of Carabida? in other respects. A still more important differential 

 character has been recently discovered by Dr. D. Sharp, namely, in the relations of the chief 

 side-plate of the metasternum to the sockets of the haunches of the middle pair of legs. This piece 



DYTICI'S MARG1NALIS. 



