INSECT ENEMIES OF WESTERN FORESTS 181 



Key to Diagnosis of Insect Injury to Wood and Wood Products 



A. Insects attacking green, unseasoned, or seasoning wood, living or 



dying trees, or freshly felled trees or logs, and projecting their 

 tunnels directly into and through the wood. 



1. Small, circular, open pinholes, often surrounded by dark 



stains; diameter uniform and less than % inch; made 

 by small, brown, shining, cylindrical beetles 



Ambrosia beetles, p. 182 



2. Large, more or less circular holes in wood; diameter more 



than Vs inch; lightly filled with pellets; wood stained 

 or not. 



a. Nearly circular holes of medium size in wood of 



broadleaved trees made by caterpillars 



Clear-wing moths, p. 200 



b. Very large irregular holes V% to 1 inch in diameter 



in broadleaved trees, usually lined with a silky 

 yellowish-brown web Carpenter moths, p. 198 



3. Circular, oval, or irregularly shaped tunnels of varying 



width gradually increasing to more than x /s inch in size; 

 usually tightly packed with fine boring dust or coarse 

 frass, except at ends occupied by larvae or pupae. 



a. Tunnels flatly oval, usually tightly packed with 



arc-like layers of sawdust-like borings and pellets 

 of woody excrement, and surface of wood marked 

 by fine, transverse, crescentric lines; made by 

 slender, white, legless grubs shaped like horse- 

 shoe nails with very wide, flat segments back of 

 head; first segment with a well developed plate 

 on both upper and lower surfaces, upper plate 

 marked with a central line, groove, V or Y 



Flatheaded borers, p. 187 



b. Tunnels broadly oval to nearly circular, tightly 



packed with sawdustlike borings and pellets of 

 wood excrement; made by long, thick, white, 

 apparently legless grubs, with horny plate on top 

 of first thoracic segment, which is somewhat 

 enlarged Roundheaded borers, p. 191 



c. Perfectly circular holes in wood, not evident in 



cambium, made by long, white, cylindrical grubs 

 with small heads, fleshy lobes for thoracic legs, 

 and the abdomen terminating rearwards with a 

 sharp horny prong 



Horntails and certain Coleoptera, p. 200 



B. Insects attacking living trees and causing black checks, pitch 



pockets, pitch flecks, gum spots, or ring distortion, but not 

 causing pinholes or wormholes 



1. Black checks showing in wood of conifers, surrounded by 



curled or distorted wood Bark maggots, p. 201 



2. Birdseye pitch flecks in pine Pitch midges, p. 70 



3. Double rings, distorted rings, retarded growth 1 . .Defoliators, p. 75 



4. Pitch pockets, gum spots, and pitch streaks in coniferous 



woods Bark beetles, p. 129 



Flatheaded borers, p. 169 



Pitch moths, p. 178 



Terminal-feeding insects, p. 35 



