66 COLEOPTERA. 



being specifically lighter than the water, rises 

 when the animal is perfectly at rest, but rises 

 tail foremost. In this situation, with the tail 

 above the water, but the head beneath, the 

 Dytiscus raises the end of its wing-cases, a va- 

 cuum is formed, a bubble of air rushes under 

 and forward, the head becomes buoyant, and 

 the insect breathes. The return to the bottom 

 is easily managed ; the wing-cases are pressed 

 against the body, the air is expelled, and the 

 legs are put in motion. 



The Dytisci are carnivorous, and are per- 

 petually chasing other insects, which they seize 

 with their fore-feet, and devour with voracity. 



The larva is very singular in its appearance, 

 more resembling a shrimp than any thing else. 

 It has a strong pair of forceps, and such a dis- 

 position to use them, that the larger sortrfiot 

 only attack other water-insects, but are said to 

 destroy the young fry of fish, which it seizes 

 with violence, and presently overcomes. The 

 chrysalis, which is found in the soft earth on 

 the banks of the water, changes in about three 

 weeks, and is succeeded by the perfect insect. 



