254 



NATURE STUDY AND LIFE 



By far the favorite hosts of these flies are the leaf-eating cater- 

 pillars and the numbers destroyed in a single season by these para- 

 sites is quite beyond computation. I have seen vast armies of the 

 army-worm, comprising unquestionaljly millions of individuals, and 

 have been unaiile to find a single specimen which did not bear the 

 characteristic eggs of a tachina fiy. These flies were present in such 

 numbers that their buzzing, as they flew over the army of caterpillars, 

 could be heard at some distance and the farmers were unnecessarily 

 alarmed since they conceived the idea that the flies were the parents 

 of the caterpillars and were flying everywhere and laying their eggs 

 in the grass and wheat. As a 

 matter of fact, one great outbreal: 

 of the army-worm in northern 

 Alabama, in the early summer of 

 1 88 1, was completely frustrated 

 by the tachina flies, aided by a 

 few other parasites and predatory 

 insects. L. O. Howard, The 

 Insect Book, p. 158. 



Fig. 10. 

 Ladv Beetles 



Larva, pup^e, and 

 adults of several 

 species 



Valuable shade trees are 

 sometimes cut because they 

 are infested with caterpillars for two or 

 three years in succession. Of course 

 trees may be killed by being stripped of their leaves 

 repeatedly ; but frequently the year after the pests seem 

 to have become unendurable there may be scarcely one 

 in the whole neighborhood, all but a few having been 

 killed by increase of their natural enemies. 



Lady Beetles, Ladybirds, or Ladybugs. — These insects are 

 too familiar to require description. We may bring one to 

 class in a vial and let the children learn their next day's 

 nature-study lesson by observing what the lady beetles 

 are doing. A branch of apple or cherry covered with 



