4 The Colorado Experiment Station. 
The adult of the twig-borer is a tiny, dark gray moth. It is an 
Old World species, supposed to have come to us with the peach 
from Western Asia, and has been known in the United States since 
i860. 
Kind of Trees Affected .—The twig-borer is principally an 
enemy of the peach, and usually we hear of it in connection with its 
damage to this fruit. It may be found, however, on all stone-fruit 
trees, but shows a decided preference for the peach. In Bulletin 80, 
of the United States Department of Agriculture, Dr. Marlatt men¬ 
tions the pear among its list of food plants. The writer has never 
noted the attack of this insect upon other than stone-fruit trees. Its 
occurrence on the pear or other pome fruits is probably rare, and 
might be compared to the occurrence of the codling moth, which is 
almost exclusively an enemy of the pome fruits, in plums, peaches, 
or other stone-fruits. While cases of codling moth infesting stone- 
fruits in any numbers are rare, they were found the past season, so 
plentiful in Burbank plums of a certain orchard, that they were 
really doing considerable damage. The twig-borer, during a sea¬ 
son of abundance, might occasionally modify its habits to the extent 
of an occasional attack upon pome fruits, as the codling moth in a 
season of abundance may modify its habits and occasionally attack 
stone-fruits. 
The Larvae and Their Injury .—The larvae, as is shown in Fig. 
1, hibernate in little silk-lined chambers constructed within the 
bark and very close to its surface. Mr. Warren T. Clarke, in his 
bulletin, *states that “in the majority of cases they are found just 
beneath a thin layer of the greener cells, just below the brown bark, 
while the greater part of the burrow is in the yellowish portion of 
the cambium.” He also states, in connection with the winter bur¬ 
row within the bark, that: “The postion generally chosen on the 
tree for the purpose is the crotch formed where the new wood joins 
that of the previous year, though older crotches are occasionally se¬ 
lected.” In Colorado I have found them almost entirely in the older 
crotches and always, when found there, they have been in the brown 
portion of the bark, just as close to its surface as the hibernacula 
could be constructed. Occasionally the hibernating cells containing 
larvae, have been found underneath buds on the new growth of 
peach trees. Their occurrence in this location does not seem to be 
at all general. 
*Bull. 144, Calif. Exp. Sta. 
