112 INSECT LIFE. 



vived the winter. A new generation begins to 

 appear early in the summer, and they are most 

 abundant late in August or early in September. 

 As cold weather comes on they disappear, bury- 

 ing themselves in mud at the roots of water plants 

 for their winter sleep. But they can be kept 

 active in aquaria in warm rooms long after all 

 have disappeared from the surface of ponds and 

 streams. 



On your return from the field trip prepare an 

 aquarium with sand or gravel in the bottom and a 

 few water plants anchored in this soil. Put the living 

 whirligig-beetles into this aquarium, and cover it so 

 that the insects can not escape. 



Put in a killing bottle some specimens to be used 

 for a study of the structure of these insects. 



The Structure of Whirligig-beetles {School 

 Work). — I. Pin the specimens in your killing bottle, 

 so that they may be easily handled without injury to 

 them, putting the pin through the right wing-cover 

 a short distance from its base. 



2. Study the appearance of one of these insects 

 when seen from above. Note that the hinder part 

 of the body is covered by a pair of horny wing-cov- 

 ers or elytra, which meet in a straight line along 

 the middle of the back. This type of wing-covers 

 is the mark by which beetles are most easily recog- 

 nized. 



3. Study the head as seen from above and make a 

 drawing of this view, showing the following parts: 

 The upper lip — a horny fiap projecting from the ex- 

 treme front end of the head ; the clypeus — a narrow 

 piece extending crosswise between the upper lip and 



