124 



ANIMAL FORMS 



Many of this great group of the flies spend their early life 

 in the water or other medium acting as scavengers ; but, on 

 the other hand, numbers attack domestic and other animals, 

 and throughout their entire lives are an intolerable plague. 

 121. The beetles (Coleoptera). Owing to the ease of pres- 

 ervation and their bright colors, the beetles have probably 

 been more widely collected than other insects. Fully ten 



FIG. 76. Long-horned borer (Ergateti). Larva (left-hand figure), pupa, and adult 



insect. 



thousand distinct species are known in North America 

 alone. They are all readily recognized by the two firm, 

 horny sheaths enclosing the two membranous wings, which 

 alone are organs of flight. The mouth is provided with 

 jaws, which are used in gnawing. Some prey on noxious 

 insects or upon decaying vegetable or animal matter, and 

 are often highly beneficial ; but others attack our trees and 

 domestic animals, and work incalculable damage. 



