FIELD BOOK OF PONDS AND STREAMS 



Fig. 204. — Crawling water-beetles, Haliplus riifi- 

 collis: I, dorsal view of adult; 2, ventral view of adult 

 showing the coxse which cover the bases of the legs ; 

 3, larva which breathes air. 



in the latter part of April, Alay and June. Females of 

 Peltodytes attach their eggs to aquatic plants, mainly Char a 

 and Nitella, while Haliplus riificollis places its eggs within 

 the dead cells of Nitella. 



Fig. 205. — Larva of Peltodytes, showing the long 

 spine-like gills through which it takes oxygen from 

 the water. (From Wilson and Matheson.) 



The larvae of both genera feed upon algae and are abundant in 

 the meshes of Spirogyra through which they creep very slowly 

 or in which they more often lie inert. They are stiff, dead- 

 looking objects very easily mistaken for frayed twigs. Larvag 

 of Haliplus (Fig. 204) breathe air through the spiracles or open- 

 ings in the air-tubes; Peltodytes takes ox\'gen through long 

 jointed spines (Fig. 205) which are supplied with air-tubes. 



Predacious diving-beetles, Family Dytiscidae. — The dytis- 

 cids are the dominant family of water-beetles. The adults 

 hang head-downward from the surface of quiet waters, and 



266 



