150 THE SCOLYTID BEETLES. 



in the bark of a living tree, they are often found filled with liquid 

 resin, yet the larvae will continue their work, apparently undisturbed 

 by it. The larvae, which are stout, cylindrical, yellowish- white, foot- 

 less grubs, with broad dorsal plates on the last abdominal segments 

 armed with 6 stout spines, transform to pupae and adults in separate 

 or adjoining cells in the borings in the larval chamber, or in separate 

 cells extended from the margin or into the roof of the chamber. 

 When the broods of adults are fully developed and ready to emerge 

 they usually bore through the intervening bark and congregate in the 

 main chamber, where they mate and await the proper time for them 

 to emerge. They then bore a few exit holes, or utilize the ventilating 

 holes in the old gallery, through each of which many individuals 

 emerge. In localities where this species is abundant it sometimes 

 congregates in swarms of greater or less extent, accompanied by 

 associates, guests, and enemies (see pp. 159-160). 



ECONOMIC FEATURES. 



In general, this species is of secondary importance in its relation to 

 the death of pine timber, but occasionally it has been found in the 

 role of the primary and only cause of the death of trees, especially on 

 Long Island, New York, and in New Jersey. The principal injury, 

 however, is usually confined to the base of living pine trees. The 

 broad larval chambers separating the bark over areas of greater or 

 less extent might in many cases heal without serious harm, but the 

 dead bark, with the pitch masses on the outside and the dried resin 

 and borings beneath, offers the most favorable conditions for subse- 

 quent injuries by forest fires, and thus these larval chambers are the 

 primary cause of a very large percentage of the so-called "fire scars" 

 or fire wounds which are so prevalent at the base and lower portion 

 of the trunks of living trees in the South. If a forest fire burns the 

 bark and resin and exposes the wood, it becomes dry and is usually 

 mined by round-headed and flatheaded wood-borers. Or the wood 

 may become either pitchy or decayed, so that the next fire burns 

 deeply into it and kills a larger area of the bark. Thus each subse- 

 quent fire contributes to an extension of the wound until in many 

 cases the tree is so weakened that it is broken down by wind or 

 attacked and killed by other barkbeetles. In the aggregate, this 

 primary injury by the beetle results in very extensive losses of some 

 of the best timber. 



EVIDENCES OF ATTACK. 



The first evidences of the work of the beetle are found in fresh 

 masses of pitch, or large pitch tubes, mixed with reddish borings, at 

 or near the base of living trees and the stumps of recently felled ones. 

 Subsequent evidence, until destroyed by fire, is found in the old pitch 



