beetles push the boring dust to the outside. The larvae of certain species live and 
feed in the egg niches which they expand into so-called cradles that branch off from 
the main galleries. Others live in the main galleries. The larvae of some species 
extend the galleries and cradles made by the parent beetles. Ambrosia beetle 
galleries differ from those of other wood-boring insects in that they are of uniform 
diameter throughout, are free of borings or other refuse, and have their walls stained 
black or brown. 
Ambrosia beetles are discussed at greater length in several publications (67, 76, 
2014214221019, 800, 1232, 1356). 
The Columbian timber beetle, Corthylus columbianus Hopkins, occurs from 
Kansas to Massachusetts south to Florida and Arkansas. It breeds in various living 
deciduous trees such as sugar, silver, and red maples, sycamore, yellow-poplar, 
boxelder, basswood, beech, elm, yellow birch, and several species of oaks. Adults 
are robust, very dark brown to black, and about 3.6 to 3.8 mm long (fig. 171A). 
The front of the head of the female is broadly concave and covered with short, stiff 
hairs. That of the male is convex and almost hairless. The pronotum is broadly 
rounded and asperate in front. The elytra are shiny, striate, and coarsely and 
shallowly punctured. The declivity is armed with small tubercles. 
erseensee 
SS 
SENG 
B ‘ | ue 
F-531258 
Figure 171.—The Columbian timber beetle, Corthylus 
columbianus: A, adult; B, callow adults in tunnels in 
the wood of a living red maple. 
369 
