222 



Aquatic Organisms 



eggs are often laid on the under side of floating leaves 



of pondweeds. 



The diving beetles (Dytiscidae and 

 Hydrophilid^) are by far the most num- 

 erous and important of the aquatic 

 beetles. These swarm in every pond 

 and pool, and are among the most 

 important carnivores of all such waters. 

 They range in size from the big brown 

 Dytiscus (fig. 129) down to little fellows 

 a millimeter long. Their prevailing 

 colors are brown or black, but many of 



Fig. 130. One of the lesser forms are prettily flecked and 



the lesser diving 

 beetles, Hydro- 

 porus, seven 

 times natural 

 size. 



streaked with 

 yellow (fig. 130). 

 The eggs of the 

 Dytiscus and of 

 other members 

 of its family are 

 inserted singly 

 into punctures in 

 the tissues of 

 living plants (fig. 

 131). Those of 

 the Hydrophilids 

 are for the most 

 part inclosed in 

 whitish silken 

 cocoons attached 



to plants near the Fig. 131. Eggs of the diving beetle, 



surface of the Dytiscus, in submerged leafstalks, nearly 



ready for hatching: the larva shows 

 water. through the shell. (From Matheson) 



