216 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



Harris states that tlic eg'jis ar(» laid during July " in clusters on tlie underside of a leaf,, 

 generally near the end of a branch." He then observes: " When lirst hatched they eat only the 

 substance of the under side of the leaf, leaving the skin of the upperside and all the veins 

 uutouche<l, but as tliey grow larger and stronger they devour whole leaves from the point to the 

 stalk, and go from leaf to leaf down the twigs and branches" (Treatise, p. 425). He adds : The fully 

 grown caterpillars "rest close together on the twigs, when not eating, and sometimes entirely cover 

 the small twigs and ends of the branches. The early broods come to their growth and leave the 

 trees by the middle of August, and the others between this time and the latter part of September. 

 All the cateriiillars of the same brood descend at one time and disappear in the night. They 

 conceal themselves under leaves, or just beneath the surface of the soil, and make their cocoons, 

 ■wLich resemble those of the Unicorn Notodouta. They remain a long time in their cocoons before 

 chaiiging to chrysalids, and are transformed to moths toward the end of June or the beginning of 

 July " (Treatise, pp. 425-426). This habit of feeding exposed and living gregariously up to the time 

 of pupation proves the almost entire immunity enjoyed by this cater]>illar from the attacks of birds. 

 "We have also noticed iu Providence the simultaneous and sudden disappearance of a whole brood 

 from an apple tree at the end of September. 



Eegarding the habits of this species In California, Mr. Edwards states that lie detected the 

 caterpillars iu the fall of 1875 " feeding upon willows in the neighborhood of Mount Shasta. Six 

 caterpillars taken, all feeding close together, upon a dwarf willow, their brilliant colors giving to 

 the plant at a little divStance the appearance of a raceme of showy flowers. In a few days they 

 began to undergo their change, and by the 27th of August had all transformed. The perfect 

 insects began to appear on the 22d of December, a second followed on the Oth of January, and the 

 third on the 10th of March. The remaining specimens all died in the chrysalis state." Mr. Dyar 

 found the larvie he describes on the maple in the Yosemite Valley in August. 



The moth has been bred by Mr. Elliot from the willow, and T have found it in difterent stages 

 of growth on the willow at Brunswick, Me., in August and September. It also feeds on the 

 aspen and blackberry iu Maine. 1 have also found the cater])illar feeding on the huckleberry 

 [Vucri Ilium). 



I found the eggs with the larva^ just hatching on the leaves of the willow at Brunswick, Me., 

 June 24. The eggs were in this case somewhat scattered and few in number, and the larva' did 

 not feed gregariously. The larva* continue to hatch till the early iiart of August in Maine, as 

 August 14 I found the larv;ie in Stage II and also fully grown on the aspen. 



"This curious and well-known caterpillar was received in August from Oregon. Mr. F. S. 

 Matteson, of Aumsville, states that he found it in large numbers on a young apple tree, entirely 

 denuding the branches of leaves. This mention is made as bearing upon the geographical 

 distribution of the species. The gregarious habits of these larva> when first hatched admit of an 

 easy remedy in hand picking." (Riley, Rep. U. S. Dept. Agr., 1SS4.) 



After the second molt some of the larvfe are ichneumoued. September 2 an ichneumon larva 

 had issued from the ventral side of the caterpillar and spun a white thin cocoon; the nearly dead 

 cateri)illar was fastened by its back to the cocoon. After a day or two the caterpillar died and 

 turned whitish, the rows of black warts becoming conspicuous. 



Riley has observed the eggs in June; the larvae from June to October; the moths in May and 

 August. 



Food 2)lnuis. — Apple, cherry, plum, rose, thorn, pear, Betnla alba, willow, aspen, blackberry, 

 bramble, huckleberry [Vaccuiiwm). I have found the larva- in Maine most commonly on the 

 willow, and it is probably from this tree that the insect has migrated to our fruit trees. In 

 California it feeds on the willow (Edwards) and maple (Dyar). 



In Beutenmiiller's list, besides the fruit trees already mentioned and different species of willow, 

 he has found it on the flowering dogwood, sweet gum, i^ersimmon, snowdrop tree, bayberry, and 

 three different species of hickory. Apricot, wistaria, oak, locust, hickory, persimmon, poplar. 

 (Riley.) 



Geographical distribution. — This species has a wide range, extending throughout the Appa- 

 lachian, Austroriparian, and Campcstrian subprovinces from Maine and Canada to Missouri and 

 southward to Texas, Georgia, and Florida. 



