ENEMIES OF PLANTS. 293 



close the bottle with a cork thick enough to be 

 easily removed (Fig. 99)- 



3. Brccdino^-jars for rearing insects should be 

 prepared before the insects are collected. Place 

 about two inches of clean sand in the bottom of 

 glass fruit-jars; moisten the sand, and provide 

 covers of cheese-cloth, or mosquito-netting, and 

 narrow rubber bands to keep them in place. 



IV. Field Trip. 



Equipped with net, cyanide bottle, and empty bottles 

 for the reception of live insects, the class should make 

 afield trip to study the habitat and the habits of insects, 

 and to collect their own material for laboratory work. 



((/) Look in the grass and weeds, under leaves, stones 

 and boards, and on the bark of trees. Are some insects 

 harder to find than others? Why? Why do you find 

 certain kinds in one place rather than in another? Ob- 

 serve especially upon what plants and what part of the 

 plant each species is found feeding. Collect a portion 

 of this plant to place in the breeding-jar with this insect 

 when you get home. Notice how the plant has been 

 affected by the feeding of the insect. Are there any 

 holes in the leaves or stem ? How were they made ? In 

 what stage of the development of the insect was the 

 damage done ? (See " Water Forms," a and b) 



V. Laboratory Studies. 



I. Siiiity of the Live Insect. — Keep each species of in- 

 sect in the breeding-jars supplied with fresh food, and 

 watch each through all the subsequent changes of devel- 

 opment. 



((?) Make careful notes and drawings on each stage. 



\h) Does the insect eat the tissue or simply suck the 

 juices of its plant-food ? How does it obtain its food in 

 each stage of development ? 



