136 MISC. PUBLICATION 273, U. S. DEPT. OF AGRICULTURE 
lock and is sometimes suspected of killing such trees. It is distributed 
through the Rocky Mountain and Pacific coast regions, where it also 
is found breeding in Douglas fir, balsam firs, and sometimes in pines. 
The adults are elongated, velvety brown beetles about one-half inch 
in length and are in flight from May to August. The larvae feed in 
the bark, where they 
construct irregular, 
winding mines which 
sometimes complete- 
ly encircle the tree. 
During the later 
stages of larval de- 
velopment they may. 
enter the wood to 
pupate, or pupate in 
the bark. 
The ponderosa 
pine bark borer 
(Acanthocinus spec- 
tabilis Lec.) (fig 
67), in the larval 
stage is the large 
white grub so com- 
monly found in pon- 
derosa pines killed 
by the western pine 
beetle, and is some- 
times mistakenly 
supposed to be the 
insect responsible 
for the death of the 
trees. It also occurs 
in other pines. These 
insects are more ben- 
eficial than _ other- 
wise, in that they rob 
FicuRE 67.—Larva and work of the ponderosa pine bark the bark beetles of 
borer (Acanthocinus spectabilis). The borings are shown t h (oad Ha af (ome) d. The 
crossing those of the western pine beetle. Insert: A. . 
Male beetle; B, female beetle. All natural size. adults are Lat oe, 
speckled, gray bee- 
tles with extremely long feelers, and the female has a long, hornlike 
ovipositor extending from the end of the abdomen. 
The locust borer (Cyllene robiniae Forst.) (22, 34, 45) (fig. 68) 
is well known as an economically important insect pest of locust in 
the Eastern States and has spread as far west as Colorado and east- 
ern Washington. The adults are somewhat slender, one-half to two- 
thirds of an inch in length, black, heavily marked with yellow, and 
with reddish legs. The markings on the wing covers or elytra con- 
sist of zigzagged and broken lines, and on the thorax and body are 
narrow yellow bands. The adults appear late in summer and lay 
their eggs in the crevices of the bark. The larvae bore irregular, 
winding galleries into the sapwood and heartwood of locust and 
