AQUATIC INSECTS OF FRESHWATER 



FIG. 227. Whirligig-beetle, 

 Gyrinus affitiis. Enlarged. 



with peculiar jointed antennae, strong mandables and 

 eyes divided by the margins of the head, so that 

 they, appear to have eyes for looking into the air 

 and a second pair for seeing into the water. The 

 body is of slightly flattened oval or elliptical form, 

 the anterior legs very long and the middle and pos- 

 terior legs short, broad and flattened. The breath- 

 ing apparatus is located at the sides and back of the 

 abdomen. Small cylindrical eggs are laid in parallel 

 rows upon aquatic plants, and the larvas are narrow, 

 flat and long, somewhat resembling centipedes. 

 Each abdominal segment is furnished with gills and the caudal end has a 

 pair of breathing tubes. Fig. 229. When fully developed the larva leaves the 

 water to spin a cocoon on some near by 

 object, in which it passes the pupal 

 stage and emerges in about one month 

 as the fully developed beetle. The 

 food of the larva consists of the 

 smaller water animals; that of the 

 beetle of flies and other insects, small 

 tadpoles and young fishes. The mouth 

 parts of the beetle are developed for 

 FIG. 228. Whirligig-beetle, siting and can inflict stinging and 

 Dincutus-vUtatm. Enlarged, bleeding wounds. They are Very agilc 

 swimmers, their peculiar gyrations on the water having 

 earned for them both their scientific and popular names. 

 There are three generally distributed genera, Gyretes, of which the most 

 common species is G. simatus; Gyrinus, of which G. rockinghamensis and 

 G. affinis. Fig. 227, are most generally distributed; and Dineutus, of 

 which D. vittatus. Fig. 228, and D. assimelis are the more generally 

 distributed forms in the Eastern and Middle States. 



Pond-Beetles or Haliplids are small beetles 

 belonging to the large family of Haliplidse, having 

 oval bodies more or less pointed at each end; the 

 three most generally distributed aquatic genera be- 

 I ing Brychius of the Pacific Coast States, and Hali- 

 plus and Cnemidotus, common to almost all ponds 

 and streams on the Atlantic slope. The larvae are 

 aquatic and have a slender segmental body furnished 

 with spiny tips, the last segment bearing a long 

 single or forked caudal appendage. The most 



FIG. 229. False Water- 



milliped, larva of a 



Whirligig-beetle. 



Enlarged. 



FIG. 230. Pond-beetle or 



Haliplid, Haliplus ruficolHi. 



Greatly enlarged. 



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