SHADE TREE INSECTS 17 



In many cases this protective covering is removed by weather conditions during 

 the fall and winter. 



The 30ung caterpillars are almost black. The fuU-grow-n caterpillars are about 

 2 to IY2 inches in length. The ground color is black with a white stripe along the 

 back and irregular brownish or 3'ellowish markings on each body segment. The 

 sides are bluish with an oval blue spot nearly surrounded by black on each seg- 

 ment. 



The pupae are slightly less than 1 inch long and are dark brown. Thev are 

 enclosed in white, oval cocoons which are a little over 1 inch long and about 

 Y2 inch thick. These cocoons are made of loosely woven silken threads, and are 

 usually attached by one side to some object in a more or less protected place. 



Lije History. The insect passes the winter as a larva, or caterpillar, in the 

 egg. The eggs hatch in April and the young caterpillars feed at first on the 

 protective covering of the egg cluster but soon attack the new leaves. Within 

 a few days the larvae begin to spin a nest, usually in a fork of a branch. They leave 

 the nest to feed, and as they crawl to the leaves they spin a silken thread. When 

 the insects are very abundant the branches of a tree may become whitened by 

 these threads. In from 4 to 6 weeks the caterpillars become full grown. They 

 then leave the trees and crawl to some sheltered place where they spin yellowish- 

 white cocoons in which the>- transform to pupae. These cocoons may be found 

 in grass, under rubbish, in crevices in bark, or on buildings. The pupal stage 

 requires about 3 weeks for its completion. Soon after the adults emerge, mating 

 takes place and the eggs for the next season's brood are deposited. 



Control. During many seasons this pest is satisfactorih- controlled by its nat- 

 ural enemies. Every 10 to 12 years, however, the caterpillars reach epidemic 

 proportions and may remain at this peak for 2 or 3 years. Such periods may not 

 occur at the same time throughout the State. As a result the insect may be 

 abundant in one section of the State and comparativel}^ scarce in another. 



Artificial measures of control during periods of abundance consist of the fol- 

 lowing: 



1. Destruction of egg masses. This is an effective method. In the winter 

 these egg masses are conspicuous on the small twigs. They should be pruned 

 off and destroyed because if they drop to the ground and are allowed to remain 

 there, practically a normal hatch may result. To be eft'ective, this should be done 

 before the larvae emerge; in other words, before April. 



2. Destruction of the tents containing the caterpillars. This may be a very 

 valuable aid in the control of the pest provided it is done while the tents are still 

 small and can be easily removed. At that time the caterpillars would not have 

 done any extensive feeding. If removal of the nests is delayed until they have 

 become large, much of the damage will have been done. 



To remove the nests a stiff brush mounted on a pole, or a pole with several 

 nails driven in one end, can be employed. This instrument is inserted into the 

 nest and twisted so that the web is wrapped around it. Then the pole is removed 

 and the caterpillars crushed. This should be done on cold, cloudy days when 

 practically all the caterpillars are within the nests. 



The practice of attempting to burn the tents should be discouraged. It is 

 comparatively ineffective because many of the larvae drop to the ground, crawl 

 away, and ma}- eventually reassemble, causing further damage. Moreover, the 

 burning is apt to cause serious injury to the bark, which may be more disfiguring 

 than the work of the caterpillars. 



3. Spraying. Lead arsenate, 3 pounds of the powder to 100 gallons of water, 

 is effective and should be applied as soon as sufficient leaf surface is present to 



