338 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
leaching out of the fermenting sap so attractive to them. Removal of 
the bark is effective, but the checking caused by too rapid seasoning 
renders the wood unfit for many uses. Other notes on control have 
been given on pages 88-40. Hubbard (247) wrote on the biology of the 
ambrosia beetles in 1897, 
and general discussions 
will be found in Swaine 
(401), Blackman (38), 
and Chamberlain.’ 
The genus Corthylus 
Krich, contains several 
eastern species of shin- 
ing, dark-brown to black 
beetles 38 to 4 mm. long. 
The antennal funicle has 
only 1 segment and the 
club is very large and 
flat. The Columbian 
timber beetle (Corthy- 
lus columbianus Hopk.) 
is one of the most aggres- 
sive species of ambrosia 
beetles, as it enters the 
sapwood of living hard- 
wood trees and_ there 
breeds successfully. The 
trees are not killed, al- 
though the beetles may 
continue to breed in them 
for many years. The 
burrows, however,  re- 
main in the wood as a 
permanent defect and 
record. 
In a living tree, Hop- 
kins found the burrows 
extending back to the 
year 1479. The defects 
consist not only of the 
black-stained burrows 
Frcure 67.—Black holes in white oak made by (fig. 67) but also of dis- 
Corthylus columbianus: A, slightly enlarged, COlorations extending 
B, slightly reduced. above and below the gal- 
leries for a considerable 
distance, varying with the species of wood. In yellow poplar these 
stains are responsible for the condition known as “calico-poplar.” 
Various hardwood trees are affected, including yellow poplar, various 
oaks, beech, birch, maple, and boxelder. The insect has been reported 
from Massachusetts and Michigan and is common in Maryland, Vir- 
ginia, and West Virginia. C. punctatissimus Zimm. is smaller than 
C. columbianus, being little more than 38 mm. long. Its range is from 
*® See footnote 22, p. 302. 
