ORCHARD BARKBEETLES AND PINHOLE BORERS. 2; 
eases, overbearing, starvation, injury to roots or base of trunk by 
other insects, mice, or rabbits, injury by the San Jose scale, or some 
other cause more or less obscure. 
The pinhole borers or ambrosia beetles, which are somewhat similar 
to the foregoing in size, color, and form, penetrate farther into the 
wood than do the barkbeetles, and, like them, prefer to attack dis- 
eased or dying trees. Beetles of this group sometimes bore into the 
twigs of live apple and pear trees, causing a dying back of the tips 
as though from twig blight. They have also been recorded as injur- 
ing nursery trees by boring into the trunk and causing that part 
of the tree above the point of injury to die. 
THE FRUIT-TREE BARKBEETLE, 
HISTORY AND GEOGRAPHIC RANGE. 
The fruit-tree barkbeetle, or shot-hole borer (fig. 2), probably was 
introduced accidentally into America from Europe some time pre- 
Fic. 2.—The fruit-tree barkbeetle (Scolytus rugulosus) : a, Adult, or beetle ; 0, same in 
profile; c, pupa; d, larva. All enlarged about 10 times. (Chittenden.) 
vious to the year 1877. The insect is now known to occur through- 
out practically all the United States east of the Mississippi River, 
and has become established in many localities to the west and also in 
Canada, although it does not appear at the present time to have 
reached the Pacific Coast States. 
TREES ATTACKED. 
The fruit-tree barkbeetle attacks and breeds in most of our culti- 
vated deciduous fruit trees and in several species of uncultivated 
pome and stone fruits. The list of food plants is known to include 
apple, pear, plum, peach, cherry, quince, apricot, nectarine, wild 
cherry, chokecherry, wild plum, mountain ash, loquat, and service 
berry. Under favorable conditions multitudes of the beetles may 
develop in the wild trees mentioned and migrate in destructive num- 
bers to near-by cultivated orchards. 
LIFE HISTORY AND HABITS. 
The adult, or beetle (fig. 2, a, b), is about one-tenth of an inch in 
length and of a dark brown or black color with dull reddish mark- 
1 Scolytus rugulosus Ratz.; order Coleoptera, family Scolytida, 
