THE GENUS DENDROCTONUS. 
147 
on the dorsal plates of the last abdominal segments, do not make 
separate larval mines, but all feed together and eat out cavities in 
the inner bark from a few inches square to several feet square. They 
transform to pupae and adults in separate or closely- joined cells in the 
inner bark or inner portion of the outer bark, but a few of the larvae 
sometimes excavate independent mines beyond the social chamber 
for the purpose of pupating. The broods work independently of 
other species and occupy and separate the bark around the base of 
trees and stumps, often extending their work for a foot or more 
under the bark onto the roots beneath the surface. The broad lar- 
val chambers are often filled with semiliquid resin without injury to 
the occupants. The attack on living 
trees and on stumps of those recently 
felled is indicated by large masses of 
pitch and pitch tubes, mixed with red- 
dish borings. 
SEASONAL HISTORY. 
Northern Section. 
overwintering stages. 
The winter is passed in and beneath 
the bark of trees and stumps attacked 
the preceding spring and summer, as 
parent adults, larvae, and developed 
broods. The larvae, as a rule, occupy 
the bark on the roots beneath the sur- 
face of the ground. 
ACTIVITY OP OVERWINTERED BROODS. 
The overwintered parent adults 
begin to extend their galleries or fig. 95.— The black turpentine beetle (Dew- 
emerge and excavate new Ones earlv droctonus terebrans): Adult. Greatly en- 
. . ., , larged. (Author's illustration.) 
m March or in April, depending on 
the locality, and probably continue active until June or later. 
The overwintered broods of developed adults begin to emerge from 
the bark and fly early in March, at Try on, N. C, or in April or May 
farther north and at high altitudes. Their principal work of exca- 
vating egg galleries is carried on during April and May, but is 
continued until hibernation begins in the fall. 
The overwintered broods of large larvae evidently complete their 
development and emerge in May and June, while some of the young 
larvae may not complete their development and emerge until August 
