ENGLISH: ILLINOIS TREES: THEIR INSECT ENEMIES 



31 



long, with three orange-colored stripes across each wing cover. 

 The beetle cuts through the bark to escape. After mating, the 

 female beetle deposits eggs on the bark of an elm tree. The 

 young grubs that hatch from the eggs bore into the bark. 



Control Measure 4- (end of circular) . 



Smaller European Elm Bark Beetle, Scolytus multistriatus 

 (Marsh.), fig. 25. — This bark beetle is the more important of two 



Fig. 24. — Elm borer: A, larva; B, pupa; C, adult. The larva, or grub, 

 is white and legless. The adult is a gray beetle about one-half inch long 

 that has three orange-colored stripes on each wing cover (stripes only 

 faintly visible in picture). 



species that spread the deadly Dutch elm disease in Illinois. The 

 other is the native elm bark beetle, Hylurgopinus rufipes 

 (Eichh.), which is rarely found in Illinois. 



The white, legless grub, or larva, of this beetle passes the 

 winter under the bark of an elm tree. It pupates in eaily spring 

 and transforms to the adult, a reddish-brown beetle, which drills 

 a small hole through the bark to escape. Thousands of "shot 

 holes" characterize the bark of heavily infested trees. If the 

 beetle emerges from a tree infected with Dutch elm disease, it 

 may carry spores of the disease fungus to a healthy tree, where 

 inoculation takes place when the beetle feeds in the crotches of 

 small branches. After feeding in the crotches of living elms, the 

 beetle bores into recently cut elm wood or weak and dying tree 

 trunks or branches. The female places white, spherical eggs 

 along the edges of a gallery she constructs for this purpose. 

 Small, white larvae that hatch from the eggs feed between the 

 bark and wood, producing characteristic patterns with their 



