160 MONTANA EXPERIMENT STATION. 



diverge, however, and increase in size as the growing larva gnaws 

 its way away from the main burrow. Most trequently the insect 

 lives in such numbers, with its larval galleries so closely packed to- 

 gether and so much confused with others that it is with difficulty 

 that individual galleries can be distinguished. 



The larvae transform to pupae at the end of their galleries. The 

 number of generations varies in different parts of the country be- 

 tween one or two and four. 



The species is a fairly common one in the eastern part of the 

 United States and may appear on nursery stock shipped in for plant- 

 ing in Montana. 



Fig. 9. Work of The Fruit Tree Bark-beetle in twig of apple — natural size. 

 (Chittenden, Circular 29, Sec. Series, Div. of Entomology, U. S. Dept. of Agr.) 



THE PEACH TWIG-BORER, i. 



In Montana markets one may occasionally find peaches containing 

 the larvae of this insect and from its peculiar hibernating habits it 

 is greatly facilitated in its distribution on nursery stock. 



The peach twig-borer is a pest of stone fruits and is very widely 

 distributed. From what is known of its habits it seems evident 

 that should this pest gain access to the peach, plum, and cherry 

 trees of this state much injury might result. 



The presence of this insect on nursery stock is indicated by bits 

 of frass attached to the bark frequently in the crotches of branches 

 of twigs. Each of these bits of frass covers the entrance into a 

 small burrow within which a young larva may be found. The 

 larva at this stage is of yellowish color with the head, the top of the 

 segment just behind it, and the posterior end of the body above, 

 almost black. In the spring when the shoots have begun to grow 

 the young larvae leave their hibernating quarters and bore into the 



I. Anarsia lineatella. 



