MONTANA EXPERIMENT STATION. 203 



are less than a (|iiarier ol an inch in length, go at once to the tender, 

 inner part of the bud, where they teed on the tender parts and do 

 great injury, often destroying fhe terminal growing portion of the 

 twig. If the bud be a fruit bud it likewise is destroyed, thereby 

 preventing the possibility of the production of fruit. 



The destruction of the terminal bud prevents the further elonga- 

 tion of the twig and at the same time causes some lateral bud to 

 grow into a principal stem. While in some cases such an unatural 

 growth is not a disadvantage, in many cases the result is a very 

 undesirable shape of tree. This is particularly true of young trees 

 in the nursery row. 



The larva soon makes use of one of the more advanced leaves 

 in the construction of a tubular retreat, which constitutes its home 

 and from which it emerges from time to time to feed. In feeding, 

 it draws in other leaves and fastens them together into a sort of 

 nest which is very characteristic of the species. Some of the 

 leaves become detached, but being bound to the other leaves fail to 

 drop to the ground, thereby making the nest all the more conspicu- 

 ous, because of the brown leaves among the green. A badly infest- 

 ed tree therefore has a decidedly unnatural appearance. 



The larvae continue to feed in these nests until they reach full 

 growth, when they construct cocoons in which the remarkable 

 change from the larva to the pupa and from the pupa to the moth 

 is to take place. The full grown larva is a half inch in length, nearly 

 naked and of a brown color with glossy black head and shield just 

 behind the head. See plate I, (figure 7). 



The cocoon is constructed, in many cases, in the tu1)ular re- 

 treat occupied by the larva. The walls are thickened and the ends 

 closed up, thereby preventing the entrance of parasites, while the 

 moth lies in the defenseless pupa stage. Other cocoons are made 

 at an}^ convenient place. Sometimes they occur in a fold of an 

 otherwise uninjured leaf. 



In due time, 01 about two Aveeks from the time the larva 

 changed to a pupa, the moth appears. The pupa works its way out 

 of the end of the cocoon, aided by the hook on its back, and the 

 anterior end splits, thus setting free the moth, which crawls out, 

 expands and dries its wings and flies away. In Missoula the moths 



