POND LIFE. 



121 



FIG. 98. A water-scaven- 

 ger beetle. 



115, was a successful one, there are probably speci- 

 mens of these beetles in your aquaria ; but if you do 

 not already have specimens, go 

 into the field again and sweep 

 plants growing beneath water 

 with an insect net until you get 

 specimens. 



Fig. 98 represents the largest 

 of our water-scavenger beetles ; 

 but we have in this country many 

 smaller species, and the majority 

 of them measure less than one 

 half inch in length. 



The members of this family 

 differ in habits from other com- 

 mon aquatic beetles by the fact 

 that when they rest at the surface of the water they 

 keep the head end of the body uppermost. The 

 most easily observed difference in structure is in the 

 form of the antennae. These are club-shaped (Fig. 



99); they are inserted immediately 

 in front of the eyes, and are usually 

 concealed beneath the eyes and pro- 

 thorax. Care must be taken not to 

 mistake the very long maxillary palpi 

 for the antennae; these palpi arise from the side of 

 the mouth, and are only three- or four-jointed. 



Select one of the larger species of water-scavenger 

 beetles and make a study of living specimens in an 

 aquarium, and of the structure of pinned specimens. 



Study especially the method in which they obtain 

 air, and the manner in which they carry it when be- 

 neath the water. 



FIG. 99. 



