2 FARMERS’ BULLETIN 763. 
groups: First, and most commonly injurious, the shot-hole borers or 
barkbeetles; second, the pinhole borers or ambrosia beetles. To the 
first group belong the fruit-tree barkbeetle’ (fig. 2), which occurs 
throughout the United States east of the Mississippi River, in many 
localities farther west, and in Canada, and the peach-tree barkbeetle * 
(fig. 7), which has been found in the States of New Hampshire, 
New York, Pennsylvania, Maryland, the Virginias, North Carolina, 
Ohio, and Michigan, and in Ontario, Canada; to the second group 
belong the apple wood stainer® (figs. 14, 16) and a related species * 
(fig. 15), and the pear-blight beetle® (fig. 17), of the Eastern United 
States. The species which are the most generally distributed mem- 
bers of the two groups in the United States and those of greatest 
importance from the standpoint of injury to deciduous fruit trees ® 
are discussed in the following pages. Each of them attacks several 
kinds of fruit trees, although the peach-tree barkbeetle appears to 
infest only the trees that bear stone fruits. 
NATURE OF INJURY CAUSED BY SHOT-HOLE AND PINHOLE 
BORERS. 
The shot-hole borers or barkbeetles burrow into the bark and 
slightly into the wood in both the larval or grub stage and the adult 
or beetle stage and, by extending their burrows in great numbers 
between the bark and sapwood, destroy that vital part of the tree 
known as the cambium. As a rule, sound, vigorous bark is not at- 
tacked, injury being confined to such trees as have had their normal 
health impaired by some other agency. Cases are not unknown, how- 
ever, in which the beetles have multiplied greatly in diseased and 
dying wood and have then extended their attacks to near-by healthy 
trees, causing extensive loss. The female beetles, in entering the bark 
to deposit their eggs, and, also, all the newly transformed beetles 
in leaving their pupal quarters in the wood, make small but rather 
conspicuous round holes in the bark. Numerous punctures of this 
kind very frequently appear in trees within a short time after they 
have been seriously weakened or vitally injured by some cause not 
connected with these insects. On account of the fact that these 
entrance and exit holes are apt to attract the attention of orchard 
owners, it is probable that the loss of trees is sometimes attributed 
directly to injury by barkbeetles, when, in reality, death is due pri- 
marily to some weakening of the trees caused by root or crown dis- 
1 Scolytus rugulosus Ratz. 2Phlocotribus liminaris Harris. *Monarthrum mali 
Fitch. 4 Monarthrum fasciatum Say. © Anisandrus pyri Peck. 
6 Another species, Stenoscelis brevis Boh., of somewhat similar appearance but belonging 
to another family of beetles (Calandridae), is frequently received from fruit growers who 
suppose it to be injurious. This insect is common in dead wood of apple and some other 
trees. The beetle is black and about one-eighth of an inch in length. The larva is white 
and has a row of minute black spots on each side So far as is known at present this 
species does not feed in living wood and therefore does not occur in orchards of perfectly 
sound trees. 
