ORCHARD BARKBEETLES AND PINHOLE BORERS., 5 
days the larve attain full growth and pupate within specially con- 
structed cells just beneath the surface of the sapwood. 
The pupal period (see pupa, fig. 2, ¢) lasts from 7 to 10 days, and 
at its termination the beetles that have developed gnaw out through 
the bark, making their escape through small, round holes (fig. 1) 
similar to the entrance holes made previously by the females. 
Within a few days after emerging these young beetles begin to 
deposit eggs, giving rise to a second brood of larve which feed in 
the trees during the latter part of the season. In approximately the 
northern half of the territory over which this barkbeetle is found 
the second-brood larvee winter in the trees, pupating early in the 
spring following. In the southern part of the territory, however, 
these larvee become adults before winter, escape from the trees, and 
deposit eggs, providing thereby for a third brood of larve. Thus, 
in the Northern States there are two generations of the insect 
annually, while in the South three and possibly four generations 
may occur within the year. 
FEEDING HABITS. 
Except in cases where the barkbeetles are excessively abundant, 
they do not normally attack and breed in healthy trees, neither do 
they feed and deposit their eggs in wood that is entirely dead. 
Trees that have been greatly weakened by unfavorable conditions, 
or that are in the act of dying, afford the most acceptable food for 
the beetles and their larve. Where there is a great quantity of 
dying wood, such as prunings and trees that have been injured by the 
San Jose scale, the yellows, freezing, or root troubles, the beetles will 
breed in great numbers, and after their supply of preferred food 
has been exhausted they will sometimes attack vigorous trees that 
may be growing in the vicinity. At first the attacks may not make 
much impression on sound trees, but a continuation of the injuries 
may eventually weaken the trees to such an extent that they become 
acceptable food for the larvae, which can then develop within the 
bark, and after this the death of the tree is reasonably sure to 
follow very soon. 
When healthy peach, plum, cherry, and other stone fruit trees are 
attacked, the flow of gum (fig. 5) will often check the entrance of 
the beetles and will prevent the development of larva in cases where 
eggs are deposited. The formation of gum at the wounds will 
diminish, however, as the tree is weakened, and after a period during 
which slight but numerous injuries have been inflicted by the beetles 
the condition of the tree may become exactly right for the deposition 
of eggs and the growth of the larve. The trunk, branches, and 
twigs of suitable trees are attacked and all the inner bark and the 
