120 APPLE AND WALNUT LEAF-0RUMPLER8. 



The larvae themselves are small, almost naked or hairless worms, and 

 bear a close resemblance to each other, dift'ering only slightly in size 

 and color; those of the nebulo being a little larger and usually of a 

 reddish-brown color, while those of the juglandis often incline to a 

 dull green. They both inhabit cases which they construct of web, into 

 which is compactly woven the little hard, dry particles of their castings. 

 The cone of the nebulo is of a brown color, a spiral or twisted form, 

 and is often attached by its whole broad side to the twig. That of the 

 juglandis is of a slate-black color and more compact structure ; of a 

 straight form, and invariably suspended by its smaller extremity. The 

 cases of the nebulo are sometimes attached directly to the twig, lying 

 around it in a spiral form, but they are usually found in companies, or 

 two or three in a clump of crumpled and partially eaten leaves ; but in 

 this case they take the precaution to anchor their cones by a strong 

 silken cable to the permanent twig from which the leaves proceed. 



The habits of the larva of the black-walnut species is in striking con- 

 trast with this. As soon as the leaves are about half grown, in the 

 spring, it leaves the twig to which it has been attached through the 

 winter, and passes out upon the central or common leaf-stalk of the 

 long pinnate leaves of the black-walnut, usually to about the middle of 

 its length, and suspends its case invariably between the bases of two 

 opposite leaflets, and these it draws down and ties together so as to form 

 a kind of roof above it. Upon these leaves it feeds, always commenc- 

 ing with the tips, so as not to disturb the connection of the leaf with 

 the stalk. I have seen at least a hundred of these larvae in their cases, 

 but never saw but one on the same leaf. 



It is an unsettled question whether the larva takes its case with it, 

 when it migrates, or leaves it and constructs a new one. Mr. Walsh 

 speaks of the larva of P. nebulo^ as traveling from limb to limb, and 

 carrying its case with it. But he gives no details, and leaves it doubt- 

 ful whether he had actually seen the insect so migrating, or only in- 

 ferred that it did so. It is the instinct of these insects t© tie their cases 

 securely to the tree, and they could not move them from place to place 

 without an elaborate separation ; and that they are capable of construct- 

 ing a new cone, I have repeatedly proved in the case of the larvae of 

 the F. juglandis^ by taking them from their cones and placing them 

 naked upon another leaf. In the course of twenty-four hours they \ 

 were ueuallj found to have constructed or commenced, at least, a new 

 cone, locating it in the ordinary position, at the junction of two oppo- 

 site leaflets. 



