12 MASS. EXPERIMENT STATION BULLETIN 353 



many trees. The young caterpillars which hatch in August and skeletonize the 

 leaves do not harm the trees to any extent because the growing season is almost 

 completed. The growth of the trees may sometimes be checked because of the 

 webs formed on the terminal parts of the branches. 



In addition to the injury done to foliage, the moths and caterpillars constitute 

 a nuisance to man and animals. Their bodies bear barbed hairs which are hollow 

 and contain a poison which affects the blood corpuscles. When these hairs come 

 in contact with tender skin, they cause severe irritation which produces a rash 

 and swelling. The hairs may be blown by the wind for a considerable distance 

 and poison people by touching them directly or b\^ getting into clothing hung 

 out of doors. If any of the hairs are inhaled, serious internal irritation may 

 ensue. 



Description. The moths of both sexes are pure white except for the tip of 

 the abdomen which is covered with brown hairs. The female is slightly larger 

 than the male. 



The eggs, which are laid in irregular masses on the under side of leaves, are 

 covered with brown hairs from the body of the female. The masses vary in size 

 and shape, being from J^ to |^ inch long and about ^i inch wide. 



The full-grown caterpillars may attain a length of Ij/^ inches. They are brown 

 with light brown hairs. Along each side there are white markings which from 

 above give the appearance of a series of white dashes. On the top of both the 

 ninth and tenth body segments there is a red tubercle. 



The pupae are about 3^ inch long and dark brown in color. They are in cocoons 

 which are enclosed in a few leaves that have been webbed together. 



Life History. In early July the female moths lay their eggs in brownish 

 clusters on the under side of leaves. They are on the wing about two weeks. 

 About mid-August the eggs begin to hatch and the young caterpillars feed in 

 groups on the surface of the leaves, skeletonizing them. The larvae molt once 

 or twice and then, about September, the caterpillars which hatched from the same 

 egg cluster begin to draw together with silken threads several leaves near the tips 

 of a branch and fasten them to the twigs. They pass the winter in these webs. 

 In the spring, about the time the buds begin to develop, the caterpillars leave 

 their winter webs and feed upon the bud scales and small leaflets. Only the larger 

 leaf veins are left. Blossoms and the fruit of some trees may be eaten when the 

 caterpillars are abundant. The larvae reach maturity about the middle of June. 

 Each caterpillar then fastens together a few leaves with silken threads and spins 

 a cocoon inside, pupating within it. Sometimes several cocoons are found together 

 in the same bunch of leaves. Two to three weeks may be spent in this stage. 

 The moths begin to emerge in early Juh- and soon la\' their eggs. 



Control. The foliage may be sprayed with lead arsenate in August when the 

 young caterpillars begin to feed on the leaves. This is the usual time to apply 

 the spray because in the spring the older caterpillars often eat the leaves as fast 

 as they appear so that not enough leaf surface is present to hold a poison spray. 

 Not less than 3 pounds of lead arsenate to 100 gallons of water should be used. 

 A sticker may be used on shade or ornamental trees but should not be applied to 

 fruit trees, especially early fall varieties, because of the spray residue which would 

 be left on the fruit. 



In the winter the nests may be cut off and burned. This is a very effective and 

 satisfactory method when it can be put into effect. 



Burgess, A. F. U. S. Dept. Agr. Farmers' Bui. 1623. 1930. 



F'ernald, C. H., and Kirkland, A. H. Hatch Exp. Sta., Mass. Agr. Col. Spec. Bui. 1897. 



