NYMPHALINAE: BASILARCHIA ARCHIPPUS. 273 



the balm of fiilcad (P. balsainifera, L., var. caudicans Ait.), aspen (P. 

 tremuloides ^liehx.), cotton Avood (P. monilifera Ait.), and Lombardy 

 poplar (P. dilatata Ait.). Populus seems to have a greater attraction than 

 Salix, thou<>h by no means, it appears to me, to such an extent as 

 Mr. Edwards finds in his experience. He writes : 



At Coalburgh, the larvae . . . feed on willow, and no aspen grows in tliis part of 

 the state [W. Va.]. In the Catskills, both willows and aspens abound, and there 

 this species prefers to feed on the latter. I have often found their cases on young 

 aspens late in the fall, but never on willoAV, though willow would be used if there was 

 no choice. In 187G, I brought several small aspens to Coalburgh . . . and since that 

 time I And many larvae . . . feeding on the leaves ; but on the willows near by, on 

 which I had been accustomed to find them, I rarely have met one. Here was a case 

 where perhaps for hundreds of generations neitlier caterpillar nor butterfly could have 

 seen an aspen, but the moment one was produced, the buttei'fly knew what would suit 

 the caterpillar best, and deserted the Avillow" (Butt, N. A., ii.). 



Boisduval and LeConte state that it is found on several species of 

 Prunus, which is partially verified by Walsh, who say it feeds occa- 

 sionally on plum, and Saunders adds cherry to the list. Mr. Lintner has 

 also taken it on apple, and Abbot figures it on Chrysobalanus oblongi- 

 folius INIichx., a rosaceous shrub of the pine barrens of Georgia. Kirt- 

 land even asserts that it is found on several species of oak and specifies 

 Q. rubra L. Possibly the close resemblance between the different cater- 

 pillars of this genus may have misled some of these observers, especially 

 in the case of oak. liiley states that specimens transferred from golden to 

 black willow become much darker in color. 



Habits of the caterpillar. On hatching, the caterpillar eats its way 

 out of one side of the egg leaving the summit intact, but, under natural 

 conditions, before attacking the leaf devours the shell to the very base. It 

 now eats first the apical leaves (81 :7) , and then those next in order, 

 omitting none in its passage down the stem, so that, as Lintner says, its 

 position may be "at once revealed by the twig upon which it had fed . . . 

 [being] entirely defoliated from its tip about eighteen inches downward, leav- 

 ing only the footstalks remaining." It is solitary in its habits, although 

 Mr. Lintner has found as many as five specimens on one small bush of 

 P. tremuloides, and I once discovered fourteen eggs on one poplar. It 

 moves about, particularly in early life, with a spasmodic motion and when 

 disturbed, snaps its head upward repeatedly. 



I once rested a leaf, on which a larva had just changed its skin for the 

 first time, upon another in such a way that the eaten tip of the first just 

 touched the last ; the caterpillar which was eating its old skin with its tail 

 toward the tip of the leaf, seemed at once to become aware of this and 

 showed unmistakable signs of temper, lashing its head to one side and the 

 other, dashing it while doing so against the leaf and finally arching its 

 body and remaining immovable as if moody. It was a long wliile before it 

 would resume its semi-cannibalistic feast. 



