INSECTS AND BIRDS. 287 



they prevent the caterpillars from reaching injurious 

 numbers in the average season. Indeed, in Texas and 

 Louisiana, where the boll weevil occurs, the caterpillar 

 is welcomed, if it does not appear in large numbers 

 until in September or October. By destroying the 

 squares and leaves of the cotton plant in the fall, the 

 caterpillar destroys the breeding places and food of 

 the boll weevil, with the result that there are less of 



COTTON-WORM MOTH. 



a, with wings expanded inflight; b, wings closed. After Riley, U.S. Dept. of Agriculture. 



the latter insects to pass through the winter and at- 

 tack the following season's crop. 



Methods of Control. The cotton caterpillar is 

 easily killed with arsenical poisons, and when they ap- 

 pear as early as July or August, measures must be 

 taken against them. Paris green has been extensively 

 used for this purpose, at the rate of about one pound 

 per acre, the " green " being applied by dusting it from 

 cloth sacks attached to a pole which is carried through 

 the fields on horseback. The more modern treatment 

 is to use powdered arsenate of lead, applied in the 

 same way. The latter substance does not cut short the 

 cotton fruitage as does Paris green, and can be safely 

 used at the rate of from three to five pounds per acre. 

 One application is usually sufficient to hold the insect 

 in check. 



EXERCISE. During the latter part of summer have the pupils search 

 for the caterpillars in adjoining cotton fields and bring to the school 

 living larvae. Feed these on green cotton leaves until they reach 

 maturity and transform. Note the manner in which the pupa is 

 formed. Keep the pupae in a glass jar and note the time required 

 for transition through this stage. What changes take place in the 

 adult moth just after it leaves the pupal skin? 



