62 



extent of 19 per cent., and in the third year at two and a half times that 

 rate. Maize should therefore not be gvown. for more than two years 

 on the same ground where this pest is prevalent. 



Observations made to determine whether the beetles found feeding 

 on clover flowers, etc., outside the maize fields from which they have 

 emerged, oviposit before leaving them or return later to do so, have 

 produced no definite results. No trace of injury or under-ground 

 infestation of any other plant than maize was found, even when tha 

 roots of such plants were intermingled with those of badly infested 

 maize. 



Glenn (P. A.). The San Jos6 Scale {Aspidiotus perniciosus, Comstock). 

 — Tiveniy- eighth Report of the State Entomologist for the State of 

 Illinois, Urbana, 1915, pp. 87-106, 2 figs.. 4 plates. [Received 

 2nd December 1916.] 



The San Jose scale is known to infest about one 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 

 dangerous ; while on a third class it cannot permanently maintain 

 itself. Some of the more important trees and shrubs which are likely 

 to be seriously injured are : — 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 infested 

 trees, but are rarely seriously injured : sour cherry, Kieffer pear, 

 blackberry, raspberry, dewberry, mulberry, grape, maple, chestnut, 

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

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

 honeysuckle, sumac, smoke-tree, and Wistaria. 



The following seem to be exempt from attack : red bud, yellow 

 wood, Kentucky coffee tree, hickory, butternut, sweet gum, tuhp 

 iron-wood, button-wood, oak, Ailantlms, papaw, barberry, Mahonia,. 

 trumpet-vine, bitter-sweet, button-bush, filbert, hazelnut, Weigelia, 

 huckleberry, witch-hazel, English ivy, Hydranxjea, gold-flower^ 

 matrimony-vine, mock-orange, and evergreens. Wild crab-apple and 

 hawthorn and a few of the other more or less susceptible trees and 

 shrubs are likely to become infested when growing near orchards, and 

 it is possible that in some localities these susceptible species harbour 

 this scale in forests. Osage orange hedges are hable to become heavily 

 infested and form important foci for the dispersal of this scale. They 

 should therefore be grubbed out or kept trimmed so low that they may 

 be thoroughly sprayed. 



The San Jose scale can only be transferred from one food-plant to 

 another while in the crawling stage. The principal agents of trans- 

 ference are birds, squirrels, insects, man, domestic animals and the 

 wind. In the dormant state it may be carried any distance on nursery 

 stock, cuttings and scions. The natural agencies which materially 

 check its multiplication are climatic conditions, predaceous and 

 parasitic insects, and fungus diseases. The parasites bred from this 

 scale in Illinois in 1914 were Perissopterns jyulchellus, How., Aphelinus, 



