TYPICAL LESSON PLANS 137 



bottom of the pond. They may often be caught while 

 swimming by means of an ordinary insect net. During 

 the early spring months these beetles may be found on the 

 ground in the vicinity of electric lights. Two specimens 

 are common, the water scavenger and the cybister, a preda- 

 ceous diving beetle. These are easily distinguished from 

 each other. The water scavenger is a large, shiny black 

 beetle; while the cybister is a little smaller, more flat, and 

 has a cream-colored band extending around the body. 



General Problems. — What special adaptations have these 

 beetles that make it possible for them to live in the water ? 

 Are they harmful or beneficial to man ? 



The Cybister. — If possible study this beetle first in its 

 natural surroundings by making a visit to a pond in the 

 neighborhood. Capture some of them, bring into the 

 schoolroom, and place in an aquarium. Have the children 

 arrange the aquariums as nearly like the pond as possible. 

 Place in the bottom a few small stones or gravel, some of 

 the decaying vegetable matter, and a stick leaning against 

 the side of the jar. If you have no aquarium use a glass 

 jar or a large glass dish. Two or three ten-cent glass 

 fruit dishes will be found valuable aids in the study of 

 many water animals. Have the children observe the be- 

 havior of the beetles. Where do they stay; at the surface 

 of the water or at the bottom? Shade one side of the 

 aquarium and determine whether they prefer light or dark- 

 ness. Do they move around much if left undisturbed? 

 Try to determine when the beetles are more active; during 

 the day or during the night ? For detailed study place the 

 beetles singly in tumblers about two thirds full of water. 

 Two or three pupils may observe the same specimen. 



