THE GENUS DENDROCTONTJS. 



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 (Den- 

 emerge and excavate new ones early droctonus terebrans): : Adult Greatly en- 

 & J larged. (Author's illustration.) 



in March or m 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 Tryon, 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 



