SOME INSECTS INJURIOUS TO ORCHARD FRUITS 545 



breeding of the pest in them and its spread to healthy trees. 

 " Another form of injury is the destruction at the beginning of 

 spring of small twigs, together with the leaves which they bear. 

 The beetles are also reported to destroy leaves by boring into the 

 base of the buds at their axils." The holes in the bark are caused 

 by the exit of the small parent beetles and by their subsequent 

 entrance to deposit eggs. The adult beetle is about one-tenth 

 inch long, by a third as wide, and of a uniform black color, except 

 the tips of the wing-covers and parts of the legs, which are red. 

 Life History. The beetles emerge from the trees in April and 

 May in the Middle States. The female burrows through the bark, 

 and partly in it and partly in the sap-wood she eats out a vertical 



a c d 



FIG. 396, The fruit-tree bark-beetle (Scolytus rugulosus): a, 6, beetle; c, 

 pupa; d, larva enlarged. (After Chittenden, U. S. Dept. Agr.) 



gallery or brood chamber, along the sides of which at short inter- 

 vals she gnaws out little pockets in which she places her eggs. 

 The larva? hatching from these eggs excavate little side galleries, 

 which branch out and widen as the larvae increase in size (Fig. 

 397) . The larvae become mature in about three weeks, when they 

 form cells at the ends of their burrows and transform to pupae, 

 from which the adult beetles emerge about a week later. There 

 are probably three generations a year in the Middle States accord- 

 ing to Dr. Chittenden. 



Were it not for the effective work of parasitic and predaceous 

 insects which prey upon it, this insect would be a most serious 

 pest. One of the most valuable of these is a little chalcis-fly * 



* Chiropachis colon Linn. 



