486 TRANSACTIONS OF THE 



The Carahii are very numerous, are insectivorous, terrestrial, 

 commonly inhabiting moist places, under stones, or [ 2 ] fallen 

 trees, under bark or on flowers, &c. They generally run briskly 

 when disturbed, and many species diffuse a foetid odor, or dis- 

 charge a peculiar, pungent, acetous gas. 



The Di/tiscii are much less numerous than the preceding, but 

 are equally nourished by animal food. They inhabit the waters, 

 occasionally visiting the surface for the purpose of respiration ; 

 they move with rapidity and ease through the water and the air 

 but on land their gait is embarrassed by the natatory form of the 

 posterior feet. 



The Gyrimi, which are now included in the same family with 

 the Dytiscii, are comparatively few in number of species, and 

 those few are so intimately united in nature by a similarity of 

 character and habit, that no division has yet been found neces- 

 sary in the genus, which still remains unchanged as it was first 

 established in the artificial system. These insects, like those of 

 the preceding Linnsean genus, are insectivorous and aquatic; they 

 do not, however, like them, remain at the bottom to seek their 

 prey, but chiefly confine themselves to the surface. They de- 

 scribe graceful curvatures or gyrations on the surface of the water 

 with a pleasing facility of movement, without exhibiting to the 

 eye the oar-like feet by which that celerity is effected. When 

 alarmed, they dive to the bottom with swiftness, carrying with 

 them a globule of air, that their respiration may not be suspend- 

 ed. When irritated, they eject a lactescent fluid, which, in 

 many instances, diffuses an agreeable odor, somewhat similar to 

 that of the CaJycanthus fioridus of botanists. They fly with 

 much ease and chiefly at night, but their movements on land are 

 uncouth and embarrassed. 



After thus briefly noticing the most prominent features exhib- 

 ited by these insects, it may be proper to observe, that the de- 

 scriptions are drawn out from such specimens only as have fallen 

 under my own observation, and which I had an opportunity of 

 examining and comparing together, in order the more effectually 

 to indicate their differential characters. The individuals are 

 chiefly preserved in my cabinet ; and for such as I do not pos- 

 sess, I have carefully referred to those collections from which I 



[Vol. II. 



