" WATERoSCAVENGER " BEETLES. 



The two principal genera are Gyrinus (length less than 

 .35 in.; the triangular piece, scutellum, between the 

 bases of the closed elytra distinct) and Dineutes (length 

 .4 in., or more; scutellum hidden). Dineutes mttatus: 

 .5 in. or longer; sides of pronotum and elytra with an in- 

 distinct, bronzed, submarginal stripe. D. discolor: about 

 .5 in. long; above very dark, almost black, bronze, shining; 

 below, yellowish. D. emarginatus: less than .5 in. long; 

 above and below black, slightly bronzed, and not very 

 shiny; middle and hind legs, narrow margin, and tip of 

 the abdomen, paler. D. assimilis: length a trifle under 

 .5 in.; above black, strongly bronzed; beneath black, 

 very shining; abdominal segments often tinged with brown; 

 legs brownish yellow; is a common species with an apple 

 odor. 



The CLAVTCORN series starts here and includes the 

 families to, but not, the Elateridas. Only Hydrophilidae 

 are aquatic. 



HYDROPHILID/E 



These are called Water-Scavenger Beetles. The 

 adults do feed on decaying material but they also eat 

 water-plants and living animals, and, furthermore, not all 

 are aquatic; the larvae are largely predaceous. The 

 adults have five joints in each tarsus, but the first joint is 

 often very small. The eggs of Hydrophilus are usually 

 laid in a floating silken case with a handle-like mast (see 

 Plate LXXIV). The silk comes from glands at the hind 

 end of the female. The larvas are much like those of 

 Dytiscus but clumsier and their tarsi never have more than a 

 single claw, while those of the Dytiscidae and the Gyrinidae 

 have two. Pupation occurs in very moist earth at the 

 water's edge; the pupa being kept from touching its cell's 

 bottom by projecting hook-like spines. Unlike Dytiscus, 

 the largest spiracles are well forward and air is taken in 

 through the notch between the head and the thorax, the 

 velvety hairs keeping out the water and the hairy club of 

 the antennae helping to break the surface film. These 

 antennae, which are less than n -jointed and broadened 

 at the tip, are sometimes overlooked by the inexperienced, 



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