341 



others are of no special interest to farmers in either way. 

 Most of the good work done by the beneficial ones con- 

 sists in aiding man in destroying the harmful ones by 

 acting as parasites. 



250. Common harmful varieties include the clothes moth, 

 bedbug, carpet beetle, cockroach, apple maggot, weevil, 

 chinch bug, corn-root worm, plant lice, currant worms, 

 potato bugs, and the 



many other pests that 

 exact a heavy toll from 

 the farmers' toil. Three 

 pests will be treated in 

 some detail, the house 

 fly, the San JosS scale, 

 and the codling moth. 



251. We place the house 

 fly first because it is so 

 well known over the en- 

 tire globe, not only in 

 the country, but in most 

 cities as well. In Chap- 

 ter IV we learned that 

 house flies breed in filthy 

 places, and are the 

 carriers of disease germs 



to man. Dr. L. O. Howard, Chief of the United 

 States Bureau of Entomology, 1 has made a long study of 

 the house fly in its relation to disease, and he has shown 

 that typhoid fever germs are carried to healthy people 

 principally by the house fly. 



If there is a microscope in the school, place a house fly 

 under it. Look for the hairs on its body and legs, and 

 for the sticky pads at the toes. You will not be able to 



1 Entomology is the Science of Insects. 



WORK OF WALNUT CATERPILLARS. 

 The leaves are eaten but the nuts are left. 



