270 BOARD OF AGRICULTURE. [Pub. Doc. 



but probably averages ten weeks. When the caterpillars are first 

 hatched from the eggs they are light in color and covered with whitish 

 hairs. In a few hours they assume a dark hue. They usually remain 

 on or near the egg cluster until they change in color, and, should the 

 weather be cold, they sometimes remain for several days in a semi-torpid 

 condition upon the egg clusters. If the temperature is favorable they 

 will search for food before they are twenty-four hours old. If a green 

 leaf be dropped upon a table on which some of the caterpillars have been 

 placed, they will all move towards it and climb upon it. During the 

 first few weeks of their existence they remain most of the lime on the 

 leaves, feeding usually on the under side. Their feeding habits are so 

 uncertain that no rule can be given which will apply to all individuals, 

 but as a rule when about half grown they begin to manifest their gre- 

 garious instincts. At that time and for the rest of their existence as 

 caterpillars they spend a large part of the day clustered in sheltered 

 situations, and feed principally at night, going vip the trees and out on 

 the branches after dark, and returning before daybreak. Where they 

 are so abundant that the food supjjly is insuflScient, they evince much 

 restlessness, and feed in numbers during all hours of the day and night. 

 They may be seen hastening to and fro, both up and down the trees. 

 Those which have fed sufficiently are at once replaced by hungry new- 

 comers, and the destruction of the foliage goes on incessantly. 



At such times the tnmks and lower branches of trees are covered 

 with a moving mass of caterpillars. Hurrying throngs are passing and 

 repassing, and nearly every leaf or denuded stem bears up one or 

 more of the feeding insects. The rustling caused by their movements 

 and the continual dropping of excrements is plainly audible. On tall 

 trees the larger caterpillars appear to crawl to the higher limbs, and 

 they seem to prefer to feed well out toward the end of the branches. 

 They do not feed gregariously except when in great numbers ; there- 

 fore they seldom strip one branch, as do the larvse of the Vanessa anti- 

 opa, but scatter throughout the trees, eating a little from each leaf. 

 Early in the season, when they are small and few in ntuubcr, their 

 ravages are scarcely noticed ; but as they grow larger and more numer- 

 ous their inroads on the tree decrease the foliage area night by night, 

 until suddenly the leaves appear to have been eaten in a single night, 

 and the tree is .stripped. 



Food Plants. 



The gypsy moth is known to destroy the foliage of nearly all native 

 and introduced trees and plants of economic importance. The list of 



