m 



The continuous multiplication of the insect is greatly checked, 

 however, in our latitude by the fact that when cold weather overtakes 

 it, nearly 97 per cent of the total product is still immature and must 

 pass the hazards of winter before its multiplication can begin. Our 

 computation of the relative numbers of males and females was based 

 on averages determined from the first representatives of each genera- 

 tion. Males predominate in the early part of the season, and it is 

 quite certain that they also predominate in the latter part, especially in 

 view of Marlatt's statement that in the hibernating group "The male 

 scales are normally vastly in excess of the females, often representing 

 95 or more per cent."=:= On this basis, out of 31,777,142 immature, 

 according to my computation, at the close of the season, only 1,588,857 

 would have been females ; and these must pass the winter successfully 

 before becoming capable of further increase. 



Food Plants 



The San Jose scale is known to infest about a hundred and fifty 

 kinds of trees and shrubs. On some it multiplies rapidly and causes 

 serious injury; on others it rarely becomes abundant enough to be 

 dangerously injurious ; and on still others it can not permanently main- 

 tain itself. 



The following are some of the more important kinds of trees and 

 shrubs which are likely to be seriously injured; apple, peach, pear, 

 plum, and sweet cherry, with their nearly related wild and ornamental 

 species ; currant, dogwood, Japan quince, June-berry, lilac, hawthorn, 

 European purple-leaved beech, flowering almond, rose, snowberry, 

 buckthorn, young poplar^ young elm, willow, mountain-ash, linden, and 

 Osage orange. 



The following become infested when surrounded by badly in- 

 fested trees, but are rarely seriously injured : sour cherry, Kiefifer 

 pear, blackberry, raspberry, dewberry, mulberry, grape, maple, chest- 

 nut, horse-chestnut, birch, catalpa, ash, locust, walnut, Virginia creeper, 

 Deutzia, Spiraea, persimmon, Althea, globe-flower, California privet, 

 honeysuckle, sumac, smoke-tree, and Wisteria. 



The following seem to be exempt from attack: redbud, yellow- 

 wood, Kentucky coffee-tree, hickory, butternut, sweet gum, tulip, iron- 

 wood, buttonwood, oak, Ailanthus, pawpaw, barberry, Mahonia, trum- 

 pet-vine, sweet-scented shrub, bittersweet, button-bush, filbert, hazel- 

 nut, weigela, huckleberry, witch-hazel, English ivy, hydrangea, gold- 

 flower, matrimony-vine, mock-orange, and evergreens. 



•Bun. 62, Bur. Ent., U. S. Dept. Agr.. p. 43. 



