AQUATIC INSECTS 907 



The little family of Haliplidae contains two genera of pretty little 

 beetles of brown color spotted with yellow, Haliplus and Peltody- 

 tes. These are easily distinguished from other beetles by the 

 sternal plates that broadly overlap the bases of the hind legs. 

 These beetles abound amid thick shore vegetation, and 

 their larvae adhere very closely to the trash, and are 

 most commonly found in floating mats of Spirogyra and 

 other filamentous algae. They are among the most 

 inactive of creatures, and in coloration and in form 

 show a high degree of protective resemblance. They 

 are easier overlooked than discovered even by the 

 collector searching for them. The stick-like larva of 

 Haliplus is shown in Fig. 1374; Peltodytes is strikingly 

 different superficially, being covered all over its body 

 by very long jointed slender bristle-like processes. 

 Matheson has recently shown that the larvae feed upon 

 filamentous algae, sucking out the contents of the cells, 

 one by one, and that the eggs are deposited by the 

 adult beetles within the coarser algal filaments. 



The dominant family of water beetles is the Dytiscidae, 

 commonly known as diving beetles. These abound in 

 all fresh-water ponds. All are aquatic in both larval 

 and adult stages, but all take air at the surface of the 

 water, with the exception of some of the smaller larvae 

 which seem to be able to absorb their oxygen from the 

 water without having developed any special apparatus 

 therefor. All are carnivorous, and in all the pupa is 

 formed on shore. 



In fitness for swimming, the adult beetles differ 

 greatly. Some of the larger forms like Cybister are 

 possessed of long oar-like hind legs provided with close- \* 3 rf'nau- 



f . 111 i i Plus. (Drawn 



set swimming fringes, and the long regular synchronous w Miss Edna 

 strokes of the legs drive the body forward with great 

 ease and swiftness; whereas, some of the lesser and more general- 

 ized forms, like Bidessus, with scanty swimming fringes, and with 

 legs otherwise little modified, either in structure or in movement, 

 from what is useful in walking, swim very poorly. These do more 



