CONSIDERATIONS FROM STUDY OF INSECTS 265 



insects or become parasites upon them, eventually destroying 

 them. The ichneumon flies are examples already mentioned. 

 They undoubtedly do much in keeping down the number of de- 

 structive caterpillars. 



Several beetles are of value to man. Most important of these is 

 the natural enemy of the orange-tree scale, the ladybug, or lady- 

 bird beetle. In New York state it may often be found feeding 

 upon the plant lice, or aphids, which live on rosebushes. The 

 carrion beetles and many water beetles act as scavengers. The 

 sexton beetles bury dead carcasses of animals. Ants in tropical 

 countries are particularly useful as scavengers. 



Insects, besides pollinating flowers, often do a service by eating 

 harmful weeds. Thus many harmful plants are kept in check. 

 We have noted that they spin silk, thus forming clothing, that 

 in some cases they are preyed upon, and support an enormous 

 multitude of birds, fishes, and other animals with food. Make 

 a balance sheet showing the benefits and harm done man by 

 insects. 



How the Damage done by Insects is Controlled. The com- 

 bating of insects by the farmer is controlled and directed by two 

 bodies of men, both of which have the same end in view. These 

 are the Bureau of Entomology of the United States Department 

 of Agriculture and the various state experiment stations. 



The Bureau of Entomology works in harmony with the other 

 divisions of the Department of Agriculture, giving the time of its 

 experts to the problems of controlling insects which, for good or 

 ill, influence man's welfare in this country. Such problems as the 

 destruction of the malarial mosquito and control of the typhoid 

 fly ; the destruction of harmful insects by the introduction of their 

 natural enemies, plant or animal ; the perfecting of the honeybee 

 (see Hodge, Nature Study and Life, page 240), and the introduction 

 of new species of insects to pollinate flowers not native to this coun- 

 try (see Blastophaga, page 45), are some to which these men are 

 now devoting their time. 



All the states and territories (except Indian Territory) have, 

 since 1888, established state experiment stations, which work in 

 cooperation with the government in the war upon injurious insects. 

 These stations are often connected with colleges, so that young 



