COLEOPTERA 



485 



Fig. 574. — Ventral aspect of part of 

 thorax and abdomen of Enchro- 

 ma gigantea: ist A, first abdom- 

 inal segment. 



Suborder POLYPHAGA* 



In the suborder Polyphaga the ventral part of the first segment 

 of the abdomen is visible for its entire breadth (Fig. 574); the first 



three ventral segments are im- 

 movably united (except in the 

 Cupesidee), and the notum of the 

 prothorax is not separated from the 

 pleura by distinct sutures. 



So far as known, the nutritive 

 cells of the ovaries are massed to- 

 gether in the terminal chamber of 

 each ovarian tube in all members of 

 this suborder. 



The larvae vary greatly in form ; 

 some are campodeiform, some are 

 scarabeiform, and others are vermi- 

 form ; in none are the legs more than 

 five-jointed, and in none are the legs 

 two-clawed. 

 This suborder includes all but the seven preceding families of the 

 Coleoptera ; the families included in it are grouped into seven series ; 

 see synopsis, page, 467. 



Family HYDROPHILID^ 



The Water-Scavenger Beetles 



The water-scavenger beetles are common in quiet pools, where 

 they may be found swimming through the water, or crawling among 

 the plants growing on the bottom. They can be easily taken by 

 sweeping such plants with a dip-net. 



They are elongated, elliptical, black beetles, resembling the pre- 

 dacious diving beetles in appearance; but they are usually more 

 convex, and differ also in having club-shaped antennae and very long 

 palpi. As the antennae are usually concealed beneath the head, it 

 often happens that the inexperienced student mistakes the long palpi 

 for antennae. 



These beetles are supposed to live chiefly upon the decaying vege- 

 tation in the water; but a number of species have 

 been known to catch and eat living insects. They 

 breathe, by carrying a film of air on the lower surface 

 of the body. This film gives them a silvery appear- 

 ance when seen from below. They obtain the air by 

 bringing the head to the surface of the water and pro- 

 jecting the antennte, which they again fold back with 

 a bubble of air when they descend. The female makes 

 a case for her eggs out of a hardened silk-like secre- 

 tion. Some species deposit as many as a hundred eggs 

 in one of these water-proof packages (Fig. 572). The 

 egg-cases in some instances are fastened beneath the 



Fig. 57; 



*Polyphaga: polyphagus, eating many kinds of food. 



