F-531255 
Figure 165.—The smaller European elm bark beetle, 
Scolytus multistriatus: A, adults (male on left, female 
on right); B, gallery pattern. 
Larvae overwinter in pupal chambers in the bark. Pupation occurs at the onset of 
warm weather in the spring and adults emerge through “shot holes” they chew 
through the bark at about the time the first elm leaves are fully expanded (late 
March to early June, depending on the latitude). Emerging adults fly directly to 
-weakened or diseased elms to breed in the inner bark or to healthy elms where they 
feed in twig crotches. It is during twig feeding by contaminated beetles that healthy 
trees are inoculated with spores of the Dutch elm disease fungus. Chances of 
infection are greatest in the spring and early summer when the long vessels of the 
tree are functioning and near enough to the surface for the beetles to cut them while 
feeding. 
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