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3- The area injuriously, infested by this insect in Illinois last 
year covers parts of at least fifteen counties, distributed throughout 
the state from the Wisconsin line to Marion county. 
4. The chief food plant is the soft maple, but linden and box- 
elder are almost equally liable to infestation. The elm and the 
honey-locust are the principal other ornamental trees subject to 
serious injury. 
5. There is but one generation of this insect each year. The fe- 
males pass the winter partly grown on the twigs of trees, and pro- 
duce eggs in late May or in June, according to the latitude and the 
weather of the season. These eggs hatch in June and July, the 
young insects establishing themselves for the summer on the leaves 
or twigs, from which they suck the sap. The males emerge as 
winged insects, and perish at the approach of winter. The females 
at that time collect on the twigs and smaller branches for hibernation. 
6. The most useful insecticide is kerosene emulsion, which, if 
used in summer, should not contain more than 10, or possibly 12^2, 
per cent, of kerosene, and, if used in winter, not more than 16 to 18 
per cent. As a summer spray this emulsion must be used twice in 
succession, with a ten-day interval between sprayings. The first 
application must be made when about half the eggs are hatched, and 
the second at about the end of the hatching period. Two treatments 
with 10 per cent, kerosene, applied to badly infested trees in Chi- 
cago, the first July 11 and the second July 20, 1905, destroyed 82 
per cent, of the scales ; a single treatment July 1 1 destroyed 64 per 
cent. ; and one July 19, 68 per cent. A similar treatment July 3, 
on the other hand, killed but 33 per cent, of the insects. 
7. A single treatment in winter with a 19 or 20 per cent, emul- 
sion destroyed more scales than two summer treatments with a 10 
per cent, emulsion, the percentages of killed varying from 86 to 
91 per cent. 
8. Where large trees weakened by unfavorable conditions or by 
insect attack are treated with strong emulsions in winter, they are 
liable to injury by a penetration of the kerosene to the roots. Such 
trees should be protected, consequently, by covering the earth be- 
neath the trees with sheets of canvas or layers of straw, or some 
similar absorbent substance. 
9. Kerosene emulsion is made as follows : Dissolve one pound 
of common soap, or half a pound of whale-oil soap, in one gallon of 
water by boiling, remove from the fire, and add two gallons of kero- 
sene. Then with a spray pump force the mixture back into itself 
for about five minutes, or until it presents the appearance of a thick 
cream and no longer separates on standing. This is the undiluted 
