AQUATIC CARNIVOROUS BEETLES; DYTISCUS. 123 



these members being flattened, and fringed with bristles, so as 

 to serve as oars. They live, during their larva and perfect 

 states, in water ; but they quit that element to undergo their 

 metamorphoses, and to pass the time of their pupa condition. 

 The larvas have the body long and narrow, with a strong head 

 armed with powerful mandibles ; and they are of very active 

 carnivorous habits. They breathe by organs adapted for aquatic 

 respiration ; but the perfect insects can only breathe air, and are 

 obliged to come to the surface occasionally for that purpose. 



The Dytiscus, the 

 principal genus of 

 this tribe, is com- 

 mon in fresh and 

 placid waters, such 

 as lakes, pools, or 

 ditches. Its larva 

 feeds upon other 

 aquatic larvse, such 

 as those of dragon- 



flies, gnats, &c. ; and moves quickly through the water, by means 

 of strokes with its expanded tail. The pupas may be found buried 

 in the adjoining banks. The Imago also is very voracious, feeding 

 principally upon the juices of the animals it attacks, which are 

 often much larger than itself ; an individual has been kept in a 

 large bottle of water for three years and a half, being fed once 

 a week or oftener with a bit of raw beef, from which it extracted 

 the blood, but being able to fast for a month at a time. The 

 other principal genus is the Gyrinus (Fig. 299), the common 

 species of which are known under the name of " Whirligigs," 

 from their peculiar motion. These may be met with, from the 

 first fine days of spring until the end of autumn, on the surface of 

 quiet waters, and even upon that of the sea, often assembled in 

 great numbers, and appearing like brilliant points. They swim 

 with great agility, often curveting in a circular direction, 

 whence their common name. Sometimes they remain stationary 

 without the slightest motion ; but no sooner are they approached, 

 than they escape by darting under the surface of the water, and 



