NATURAL ENEMIES OE THE FOREST. 



241 



The number of insect enemies of tlie forest is enormous. At the 

 St. Louis Exposition, there were on exhibit nearly tliree hundred 

 such insects. These belong to some twenty orders, of which the 

 beetles (Coleoptera) , which have horny wings and biting mouth parts, 

 and the moths and butterflies (Lejndoptera) , with membraneous 

 wings and sucking mouth parts, are the most destructive. Insects 

 attack every part of 

 the tree, the seed, the 

 shoot, the flower, the 

 root, the leaf, the bark 

 and the wood, both 

 standing and cut. 



Of the fruit and 

 seed pests, the most 

 destructive are wee- 

 vils, worms and gall 

 insects. 



Of the twig and 

 shoot pests, beetles, 

 weevils and caterpil- 

 lars are the worst. 



Among insects that 

 attack roots, the peri- 

 odical cicada (17 year 

 old locust) may be 

 noted. 



The leaf pests are 

 far more serious. They 

 include the true and 

 false caterpillars, moths, gall insects and plant lice. 



Of the bark pests, the bark beetles are the most destructive. 

 These are also called Engraver Beetles from the smoothly cut figures 

 which are their burrows under the bark. Figs. 89, 90, 91. 



Many pairs of beetles make a simultaneous attack on the lower half of 

 the main trunk of medium-sized to large trees. They bore thru the outer 

 bark to the inner living portion, and thru the inner layers of the latter; 

 they excavate long, irregular, longitiidinal galleries, and along the sides of 

 these at irregular intervals, numerous eggs are closely placed. The eggs 

 soon hatch and the larvae at once commence to feed on the inner bark, and 



Fi^^. so. Work of the Spruce Destroying Beetle: 

 a. Primary g-aUery; ^. Horint^s packed in side; ^, En- 

 trance and central burrow thru the pacK'ed borings; 

 rt, Larval mines. Note how the etrtfs are grouped on 

 the sides. [Agr/c. I'ear Hook, VWi, Fig. 24, p. 2b8. | 



