120 INSECT LIFE. 



Learn what you can regarding the habits and 

 structure of these larvae. Observe their favorite 



FIG. 97. A water-tiger. 



attitude when at rest. Learn how they obtain air. 

 Place other aquatic insects with them, and observe 

 their predaceous habits and their method of sucking 

 the blood of their victims. Note their methods of 

 locomotion. 



In studying their structure, observe the peculiar 

 form of their mandibles ; these are large, sickle- 

 shaped, and hollow, with a slitlike opening near the 

 tip. They are admirably fitted for holding the prey 

 and at the same time sucking the blood from its 

 body, as the hollow of the mandibles communicates 

 with the mouth. Observe the spiracles along the 

 sides of the abdomen ; these are used but little if at 

 all during the larval stage. The last pair of spiracles 

 are just beneath the tip of the last abdominal seg- 

 ment ; it is through these that the larva obtains its 

 supply of air. 



Preserve one or more specimens in alcohol and 

 put them with the predaceous diving-beetles in your 

 collection. 



THE WATER-SCAVENGER BEETLES (School Work).- 

 The water-scavenger beetles are common in quiet 

 pools, where they may be found swimming through 

 the water or crawling among the plants growing on 

 the bottom. If the collecting trip outlined on page 



