INSECT ENEMIES OF WESTERN FORESTS 159 
Cheilosia (11). This type of defect is very prevalent in western 
hemlock growing in western Washington and Oregon at elevations 
below 1,800 feet and is called the “black check” of hemlock. These 
defects do not impair the wood for structural purposes but render 
a high percentage worthless for finishing wood, staves, or other 
special purposes. 
The adults are small two-winged flies which lay their eggs on the 
bark of the trees, probably on the resin which exudes from feeding 
punctures made by the hemlock hylesinus. The maggots enter the 
bark, making a small wound, and feed on the sap and inner bark. 
The larvae when full grown are white maggots three-fourths of an 
inch in length, with the fore part of the body thickened and with a 
long, telescopic, protractile tail. Feeding continues for several years, 
then in the spring puparia are formed in the resin mass at the en- 
trance to the wound, and the adult flies emerge in April and May. 
Two species have been recognized as important in the West. 
Cheilosia alaskensis Hunter makes the black check in western hem- 
lock (fig. 79) and is distributed from Oregon to Alaska. C. hoodi- 
ana Bigot does similar work in white and lowland fir in the same 
region and also has been reported from New Mexico. There are 
several other species whose habits are not fully known, which cause 
similar wounds in other western conifers. 
INSECTS WORKING IN SEASONED OR DECAYING WOOD 
POWDER-POST BEETLES 
A group of beetles belonging to the families Ptinidae, Anobiidae, 
Bostrichidae, and Lyctidae are called powder-post beetles because 
the larvae burrow into hard, dry wood and reduce it to fine powder. 
There are hundreds of species in this group, many of which confine 
their attack to deadwood in the forest and are of lttle economic 
importance. Most of this group confine their attacks to the sapwood 
of the hardwoods, but a few species attack pine and Douglas fir and 
occasionally do some damage. A few work in finished products and 
are extremely destructive on account of their ability to reinfest wood 
repeatedly until it is completely destroyed and to attack any 
exposed surfaces of furniture, flooring, and sills, and thus establish 
themselves in utilized wood products. 
Great care needs to be taken in storage yards to prevent infestation 
from developing before the sapwood of hardwoods is treated with a 
filler, painted, or varnished and thus protected. Badly infested 
stocks of tool handles, oars, or building material should be burned. 
If lightly infested they can be treated by soaking in kerosene or by 
applying liberal doses of crude liquid orthodichlorobenzene. 
The Lyctus beetles (49, 74) are probably the most dangerous and 
destructive members of this group (fig. 80). The adults are small, 
flat, slender, dark-brown beetles about one-eighth to three-sixteenths 
of an inch long. Eggs are laid in the pores of the wood, and the 
larvae bore only in the sapwood of various hardwoods, reducing it to 
a flourlike powder. The insects pass the winter as larvae. Pupa- 
tion occurs in the spring, and the new adults appear early in the 
summer. In heated buildings development is hastened, and under 
such conditions adults may appear much earlier. Small round holes 
