170 MISC. PUBLICATION 273, U.S. DEPT. OF AGRICULTURE 



the inner bark and wood of many species of forest trees. Their 

 activities are diversified. A few species attack and kill healthy 

 trees by mining under the bark; others bore into the inner bark 

 and sapwood of trunks, branches, and twigs of weakened and 

 dying trees; while others breed only in dead or recently felled 

 trees and make flattened, winding wormholes through the wood. 

 A few species are leaf miners. In general, the group is a destruc- 

 tive one in that they sometimes kill living trees and often reduce 

 the value of lumber by their attacks. Others assist materially in 

 the natural process of disintegrating deadwood in the forest, and 

 these are decidedly beneficial. 



The adults are flattened, frequently brightly colored beetles with 

 a metallic luster. They fly and mate and then lay their eggs in 

 bark crevices or on the outer surface of the bark, early in the 

 spring or in summer. When the eggs hatch the young grubs con- 

 struct long, winding, oval mines in either the bark or the wood, 

 or in both (fig. 78,A). 



These mines gradually widen as the grubs increase in size, and 

 end in elongated, oval pupal cells. The slender white grubs are 

 the stage usually found in trees, and they can be recognized by 

 their long, legless bodies, shaped like a horseshoe nail. The head 

 is small, and the first segment back of the head is much broader 

 than the following body segments and has horny plates on the top 

 and bottom. Growth of the larvae continues until fall, when activ- 

 ity ceases with the advent of cold weather. The winter usually 

 is passed in the larval stage, although some larvae may pupate in 

 the fall and pass the winter as adults. Some species require 2 or 

 even 3 or more years to complete their growth. 



Since the beetles of this family have very diverse habits, only 

 those species that attack and mine the inner bark of living trees 

 are considered in this section. Species that work in the wood are 

 more important from the standpoint of forest products and will 

 be discussed in that section (p. 187) . 



For the control of flatheaded borers that mine in the inner bark, 

 the same methods are used as for bark beetles. Infested trees 

 usually are felled, peeled, and burned, and this work is frequently 

 carried on in connection with the control of bark beetles. 



The pine flatheaded borer (Melanophila gentilis Lee.) (22) is 

 commonly found throughout the Western States, working beneath 

 the bark of sugar, ponderosa, and Jeffrey pines. It is the species 

 usually found infesting felled trees and logs, windfalls, and in- 

 jured trees or occurring as a secondary species in the bole of 

 standing trees. The bright, bluish-green adults are about y 2 inch 

 long. The larvae are white, legless grubs about 1 inch long. - They 

 are primarily bark-boring in habit and rarely enter the wood. On 

 reaching maturity the larvae work out into the outer bark and 

 pupate in oval cells close to the surface. There appears to be one 

 generation annually. 



The California flatheaded borer (Melanophila californica Van. 

 D.) (159) (fig. 78) is primarily destructive to ponderosa and 

 Jeffrey pines but may be found attacking knobcone, digger, Coul- 

 ter, Monterey, and possibly other species of pine in California, 



