AQUATIC INSECTS OF FRESHWATER 



anterior legs are prehensile and adapted to aid in holding their prey. 

 The many hundred eggs are deposited in a cocoon spun by the female 

 and attached to the lower side of the floating leaves of aquatic plants or 

 drifting leaves and branches, Fig. 226, to which the female clings with 

 her posterior legs, and guards until the larvas are hatched. These also 

 somewhat resemble those of the Dy tiscidas but are thicker and have shorter 

 mandables, those of the larger genera growing to lyi or 3 inches m 

 length and ^ inch thick. They are popularly known as Spear- 

 mouths, and are ravenous feeders, destroying water insects, flies, small 

 snails, tadpoles, fishes, and their younger and weaker brethren; all of 



which they attack and 

 crush with their power- 

 ful madables to extract 

 the juices. They are 

 very destructive to young 

 fishes and will destroy 

 hundreds in a few days 

 in the hatching and rear- 

 ing tanks. The largest 

 beetles of this family be- 

 long to the genus Hydro- 

 philus of which the most 

 common species are//. /n- 

 apgularis and H. glaber. 

 Fig. 225, the next larger 

 to Hydrocharis, of which 



FIG. 226. Water Scavenger-beetle or Great Water-beetle, Hydrophilus H. OOtUSatUS IS the mOrC 

 glaber. Female attached to Egg-pouch and predaceous larva, or Spear-mouth, (^q^^^^q-^ and the Smaller 



to Hydrochus, of which about twelve species inhabit the Eastern and 

 Middle States, the more common forms being H.scabratus and H.variolatus. 

 There are a number of other genera, and some of the smaller species are 

 not aquatic but live in moist earth and manure, feeding upon Dipterous 

 larvas. The Water-scavenger beetles are nocturnal in their flights, strong 

 of wing and are attracted by lights and bright surfaces; are frequently seen 

 near electric lights and will penetrate into houses, instances being recorded 

 of their having found their way into household aquaria through open 

 windows. All of this order have short antennae, clavate or clubbed at the 

 tips and may easily be distinguished from the Diving-beetles. 



Whirligig-Beetles, also popularly known as Scuttle Bugs and Spin- 

 ners, belong to the family of Gyrinidae and occur in great numbers on al- 

 most all still and slow-flowing waters. They are brilliant bluish-black beetles 



Z70 



