122 INSECT LIFE. 



Observe their food habits. These beetles are sup- 

 posed to live chiefly upon decaying vegetation in the 

 water, but some of them have been known to feed 

 upon other insects and upon snails. 



Arrange your pinned specimens under a copy of 

 the following label and immediately after the Dyti- 

 scidas : 



Family HYDROPHILID/E (Hyd-ro-phil'i-dse). 

 The Water-scavenger Beetles. 



The members of this family form cases in which 

 the eggs are laid. Fig. 100 represents one of these 

 cases attached to a leaf. If you find 

 similar cases preserve them in your col- 

 lection with the beetles of this family, or 

 place them in an aquarium and try to 

 rear the young. 



THE LARVJE OF WATER-SCAVENGER 

 BEETLES (Field and School Work).- -The 

 larvae of the water- scavenger beetles 

 live beneath the surface in ponds inhabi- 

 ted by the adults, and may be captured by a sweep- 

 ing net in the same way as the adults. As they thrive 

 well in aquaria, their habits can be easily observed. 

 They bear some resemblance to water-tigers (Fig. 

 97), but they can be distinguished from them by 

 the following characters : the body is more plump ; 

 the mandibles are not so slender, are not tubular, and 

 are usually furnished with one or more teeth ; and 

 the abdomen, in all the species that I have studied, is 

 furnished with backward-projecting spines or with 

 filaments, or with both. 



Study the habits of these larvse. Observe the 



100. 



