ENTOMOLOGY IN OUTLINE COLEOPTER A. 99 



destructive to tent-caterpillars, climbing the trees at night and feeding 

 on them. Other species are predaceous on cankerworms and cutworms. 

 The bombardier-beetles (genus Bruchina) possess an organ at the 

 tip of the abdomen by which when disturbed they spurt out, "with a 

 popping sound and puff of smoke," an ill-smelling, 



acrid fluid. Harpalus is a large genus, any species V 



of which destroys large numbers of the larvae of the 

 codling-moth and plum-curculios. 



The Dytiseidse are a family of carnivorous water- 

 beetles of some three hundred species, common in all 

 our streams and ponds, many of them from one to 

 two inches long and quite conspicuous. They 

 possess a single pair of eyes, long, slender antennae, FIG 

 are flatly convex in shape and brown or black in 

 color; the swimming hind legs are long, broad, and heavily fringed 

 with hairs, and their air supply under water is carried in a bubble 

 under the elytra, held in by means of fine hairs. The larvae are long 

 and slender, and on account of their voracity are called water-tigers. 

 They breathe through a pair of spiracles at the top of the body, coming 

 to the surface frequently for the purpose. The pupal stage is passed in 

 a rough cocoon in the bank of the stream or pond. 



The Gyrinidse, or whirligigs, are the small, metallic, steely black 

 beetles seen swimming in circles on the surface of ponds and still pools. 

 They are peculiarly characterized by the possession of compound eyes- 

 on each side of the head, which are distinctly divided into two parts by 

 the sharp lateral margins of the head. They are of slight economic 

 value, though destroying some mosquito larvae. 



Tribe Clavieornia. 



This tribe comprises those beetles which have clubbed antennae. 



The family Hydrophilidse are the " water-scavengers," usually black 

 in color, though some have orange or red markings along the margins, 

 convex above, flattened below, smooth and polished, and possessing 

 short antennae, which are clavate or clubbed. Certain of the smaller 

 species are small, and have a rough body wall, and crawl on the bottom 

 of ponds and streams instead of swimming, and still others are land 

 forms. One species, Hydrophilus triangularis, is often seen flying about 

 electric lights. All live on decaying matter, but are of slight economic 

 importance. 



