ROUNDHEADED APPLE-TREE BORER. 6 



rence River westward through Quebec and Ontario to Minnesota, 

 thence in a southwesterly direction through Nebraska, Kansas, and 

 New Mexico to Texas, and thence eastward through Texas, Louisiana, 

 Mississippi, Alabama, and Georgia to the Atlantic coast. (See 

 fig. 1.) There seem to. be no data showing that the general range of 

 the species has been greatly extended by the development of the 

 orchard industry of the country. 



Within the bounds of its range there are many limited districts 

 where the borer does not occur, or, at least, where it is very uncom- 

 mon. Just why this is true can not be fully explained, but the ab- 

 sence of native host trees and the abundance of those species of wood- 

 pecker which prey upon the borers are two factors which often have 

 much to do with the local scarcity of the pest. Areas of comparative 

 freedom and corresponding areas that are heavily infested often 

 exist near together for years at a time with little relative change. 

 This occurs in native woods as well as in orchards. The peculiarity 

 may be partly explained by the tendency of the species to colonize or 

 form family breeding centers, far from which the adult females do 

 not habitually wander. 



FOOD PLANTS. 



Probably no other tree is so subject to attack by this borer as the 

 quince. Wherever the borer is common it is difficult to succeed with 

 this fruit. Quince trees are usually small and one or two borers 

 can injure greatly or kill a tree in a single year. The habit which 

 the quince has of sending up suckers or sprouts around the central 

 stem tends to give the borers a good chance to work. In the bases 

 of such clumps borers are hard to reach in the worming process and 

 there they may find positions where woodpeckers can not get at them. 

 Apple is undoubtedly the second choice, and probably mountain ash 

 {Sorbus ameHcana) is next in favor. Of the cultivated fruits, 

 quince, apple, and pear are preferred in the order named. Mountain 

 ash, service {Amelanchier canadensis), wild crab {Pyrus spp.), haw- 

 thorn {Crataegus spp.), and chokeberry {Aroma spp.) are native 

 hosts which are attacked about in the order stated. There are 

 records in the Bureau of Entomology of the development of this 

 borer in peach, but it is certain that this tree is very rarely attacked. 



In one instance in West Virginia all the host trees of this borer 

 which grew on a certain tract of woodland and grown-up field were 

 cut and examined to determine the relative extent of infestation of 

 each species of tree. The trees examined numbered 1,483 and the 

 results of the count are given in Table I. It is probable that in any 

 adjacent locality a considerable variation from these figures might 

 have been found, yet the results of the count showed what is ap- 



