1896.; -149 



that the little larva, having fixed its thread of silk to certain points of 

 a leaf or leaves, approximated the detached parts by the sheer force 

 of its own strength. This theory was exploded by Wilkinson in his 

 "British Tortrices" (1859), wherein he states as follows: — "The 

 folding and twisting of the leaves and twigs is accomplished by means 

 of an elastic silk, spun by the larva, usuallv of a whitish colour, which 

 hardens and contracts on exposure to the air, and thus draws opposite 

 portions of the leaves towards each other. A series of sj)innings and 

 contortions effect the end in view. The operation is therefore twofold : 

 first, the act of the larva itself; secondly, the force exercised by the 

 contraction of the silk ; there is otherwise no accounting for the ex- 

 traordinary folding and bending of stubborn leaves, obviously beyond 

 the unassisted strength of minute larvae." 



Wilkinson's observations were corroborated by my friend Bernard 

 Piffard, who, in an early number of this Magazine (Ent. Mo. Mag., 

 ii, 15), WTOte, "Now, from what I have observed, there appears to me 

 to be another reason for the approximation of the portions of leaves 

 spun together, viz., the contractile power of the recently spun web itself, 

 which certainly shrinks very considerably in a short space of time ; 

 and this must be of (at any rate) great assistance to the leaf-rolling 

 larva. That this contractility does exist can be made evident in the 

 following experiment: — having attached a small piece of paper to 

 one extremity of a newly spun thread a few inches in length, suspend 

 it by fixing the other end of the thread to a firm object, and mark off 

 the exact position of the lower end of the piece of paper. After a 

 short time it will be found that the paper has been raised, in a very 

 appreciable degree, above the mark at which its original position had 

 been indicated." 



Later on (Ent. Mo. Mag., iii, 279) I sent a note confirming the 

 accuracy of my friend's remarks, and added, that the newly spun 

 thread, when arranged as previously suggested, and damped by gently 

 breathing upon it, contracted to one-half its length in the space of a 

 few minutes. But these statements seem to me to be merely prelimi- 

 nary to a more thorough investigation of the matter, a study of which 

 can hardly fail to bring to light new and instructive facts ; there being 

 80 many points from which the subject may be viewed: — the move- 

 ments of the larva itself; the production of the silk, its nature, 

 contractility, and other properties ; its possible uses, whether for 

 other purposes besides those of defence against enemies and elements ; 

 the positions, times of day, atmospheric conditions affecting the pro- 

 cess ; and various other items. 



