Insects of Shade Trees and Their Control. 85 
and as little time as possible should be lost between the discovery of 
the insect and the application of the remedy. The spray solution 
should be directed especially at the underside of the leaves. 
BOXELDER APHIS.” 
How injurious.—This is an insect of the Middle West where the 
boxelder is its sole host. Its feeding stunts the young leaves, and its 
honeydew, together with dust and sooty fungus, soils the tree so that 
it looks most unattractive. 
How recognized—Numerous tiny, pale green, licelike insects are- 
noted on the leaves and tender twigs, and there is a sootlike covering 
on the leaves and twigs or a sticky liquid on the leaves and on the 
ground beneath the tree. Drops of this liquid also hit persons beneath 
infested trees. 
Habits—The winter is passed in the form of eggs laid on box- 
elder bark. In the spring, as buds begin to push out, the eggs com- 
mence hatching and the emerging insects migrate to the new growth, 
where they forthwith insert their beaks and begin to feed. On 
reaching maturity they begin to produce living young, each “ shell- 
ing out” as many as a hundred or more in the course of 20 days 
or so. Four or five generations thus follow one another in quick 
succession until about early June, when a generation of a quiescent, 
inactive form appears, gradually increasing in proportion to the 
others until August, when only occasional active individuals are to 
be found. The “ dimorphs,” as the resting insects are called, do not 
feed, but rest on the leaves throughout the summer, when the growth 
seems to take on a new lease on life. Early in September the di- 
morphs change to the normal, active form and produce another gen- 
eration or two of living young. All of the individuals hitherto 
spoken of are females and most of them are wingless. The last gen- 
eration of the season alone is composed of males and females, and 
the latter, after mating, deposit their eggs on the bark of twigs and 
branches, where they overwinter, thus completing the cycle. 
Remedy.—A spray of 40 per cent nicotine sulphate (p. 13) applied 
at the time new growth starts is a pretty sure and safe remedy. 
TULIP-TREE APHIS.” 
Appearance and injury.—tThe sole injury of the tulip-tree aphis 
consists in the abnormally heavy dropping of the leaves, but in a 
yard or on a street the littering of the ground is a serious objection. 
The falling tulip-tree foliage, on the other hand, usually indicates the 
presence of this insect in great numbers on the leaves. The insects 
59 Periphyllus negundinis Thos. © Macrosiphum liriodendri Mon. 
