Insect Pests of Interest to Cotton Growers 



185 



process takes place inside of a thin, white silken cocoon which is 

 formed on the surface of the leaf and in which the caterpillar, bent 

 in the form of the letter "U,"' can be faintly seen. Finally, when 

 the worm is full grown, it spins a white, ribbed cocoon about five- 

 sixteenths of an inch long. This is attached to the cotton stalk or 

 to other parts of the plant. In this cocoon it transforms first to a 

 pupa, from which the delicate, grayish white moth eventually 



Fig. 12 — Work of cotton leaf perforator on Egyptian cotton leaf (greatly en- 

 larged). 1, mine containing larva. 2. mine which ha.s been vacated by larva. 

 3, work of caterpillar after leaving leaf mine. 



emerges. These insects are subject to attack by minute wasp-like 

 parasites which some seasons keep them so reduced in numbers 

 that they are not conspicuous. So far no distinct damage to cotton 

 plants has been noted in Arizona, although it is not impossible that, 

 with a start unusually early in the season and with conditions un- 

 favorable for the activity of the parasites, some damage might be 

 done. As observed so far, however, the perforation of the leaves 

 has usually been a benefit rather than otherwise, for the same 

 reason as has been noted in the case of the partial defoliation of 

 cotton plants by the cotton leaf worm. 



