398 PROCEEDINGS OF THE NATIONAL MUSEUM VOL, 92 
gallery, in each side of which the eggs are placed in closely spaced 
egg niches. The larval mines extend out at each side, more or less 
at right angles to the egg gallery. Each egg gallery is the product 
of a pair of beetles. In some species at least, the male remains on 
guard in the entrance gallery, often dying in that position. 
In all cases where the habits are known, the young adults at the 
time of emergence from the old host are sexually immature and must 
feed for some time before attacking a new host. In some cases 
they clip off and eat the tender leaflets, thus partially defoliating 
healthy trees. The young adults derive most of their food, how- 
ever, by boring into the twigs of vigorous trees and gouging out most 
of the sapwood. This causes the twigs to wilt and die. Sometimes 
they break off entirely and fall to the ground, but more often the 
wilted twigs remain attached by a few shreds of bark and wood. 
This feeding of the newly emerged adults produces effects which 
are always very evident and often excessive in areas where the 
beetles are more than usually numerous. Even under conditions of 
nature such as in the semidesert areas of the Scuthwest, where 
junipers are among the few tree species able to survive, the wilted 
and broken twigs are very common and conspicuous. In areas where 
cupressine trees are often used as ornamentals, the feeding injuries 
may be so numerous as to detract from their beauty. In some 
cases such feeding activities kill so many twigs as entirely to ruin 
the appearance of an evergreen hedge or of a specimen tree. This 
is especially true in many areas in California and Arizona. 
While the twig feeding of the adults is responsible for most of the 
damage inflicted by species of PAloeosinus, their breeding activities 
also cause considerable injury under certain conditions. Most of the 
species are not at all aggressive in their attacks on trees but by 
preference enter the bark of dying, weakened, felled, or broken 
trees or portions of trees. However, when the beetles in flight in 
an area are particularly numerous, trees which appear healthy may 
be attacked and killed. Fatal attacks on several species of cypress in 
California by P. cupresst Hopkins and P. eristatus (LeConte) and by 
the latter species also in the Gila Valley of Arizona, have been 
numerous. It is possible that species of Cupressus are more suscepti- 
ble to attack than are species of other related genera, for in the 
vicinity of Mexico City P. baumanni Hopkins and P, tacubayae 
Hopkins attack the same tree and are known to be serious enemies 
of the local species of cypress. 
It is true, perhaps, that if most cases of killing caused by attacks 
of Phloeosinus upon apparently healthy trees were examined criti- 
cally it would be found that such trees had been weakened by drought 
or other causes. The trees’ resistance to attack had been lessened 
