ROTJNDHEADED APPLE-TREE BORER. 5 



the proximity of the insect's breeding places, the breeding places 

 quite often consisting- of these wild host trees that thrive on account 

 of favorable soil, elevation, or other local conditions. Orchards es- 

 tablished on newly cleared lands and in hilly locations are more 

 likely to have woods or neglected thickets of wild crab apple, seed- 

 ling apple, or hawthorn growing near to them than are orchards in 

 the more valuable and highly cultivated valley or level lands. The 

 wild host trees that grow in the woods and thickets (PI. I) are usu- 

 ally breeding places for the borer, and the adult insects that develop 

 within them fly to the orchards near by and deposit their eggs. In 

 some localities of the Shenandoah apple region the idea is prevalent 

 that borers discriminate between soils and prefer the shale lands of 

 the hills rather than the clay and loam of the valleys. The greater 

 abundance of borers in hill orchards, however, can be explained by 

 the prevalance in such localities of the wild trees in which they 

 breed (PL VII, C), the soil having only the indirect bearing on the 

 situation that the shale lands favor the growth of service and 

 other wild host trees. 



The native service tree (PL I) is perhaps the most effective dis- 

 tributor of this insect. In about 25 localities within the States of 

 Maine, Michigan, Pennsylvania, West Virginia, Virginia, North 

 Carolina, Georgia, Alabama, Mississippi, and Florida, where careful 

 investigations were made, the absence, scarcity, or abundance of 

 service trees was accompanied by a corresponding absence, scarcity, 

 or abundance of the roundheaded apple-tree borer. 



CHARACTER OF INJURY. 



About 95 per cent of the eggs (PL IV, B, C, E) of this borer are 

 deposited within the bark at the base of the tree trunk. (PL III.) 

 Usually the eggs are within 6 inches of the ground, but occasionally 

 they are placed in a crotch of the tree or even in a branch 10 or 15 

 feet above ground. The larva (PL V, A, B ; VIII, A) , which hatches 

 in early summer, feeds at first on the inner bark, eating out a roughly 

 circular space about the oviposition scar and ejecting stringy, saw- 

 dustlike castings of a reddish color through small openings in the 

 outer bark. (PL V, C.) As the larva develops it extends its gal- 

 lery either up or down the tree or transversely with the grain of the 

 bark and before the end of the first season may burrow into the wood. 

 (PL V, A, B.) More frequently, however, it spends the first winter 

 in the inner bark and enters the wood the second summer. The bur- 

 rows, both in the bark and wood, are broad and irregular in form, 

 and, with the exception of a space about the borer (PL VI, D), are 

 packed with digested wood particles (PL VII, A, C). The borer 

 feeds from about the blooming time of apple in the spring until late 



