174 BRITISH LEPIDOPTERA. 



larvae, however, use more than one method of disposing of their frass, 

 depositing it in one part of the mine in one way, in another part in a 

 different manner, the change in method usually indicating a larval 

 moult. The larva of X. anomalella does so. 



It has been stated that the division of the various forms of mine 

 into gallery and blotch, is more or less artificial, and that there are no 

 sharp boundaries between the various forms which frequently pass by 

 easy gradations into each other ; yet they are sufficiently constant 

 for the species to be assumed with almost absolute certainty, if 

 sufficient allowance be made for the nature of the* leaf, in those species 

 which have more than one food-plant, or the manner in which the leaves 

 differ as to the quality, texture or thickness of the parenchyma. When 

 this is so, there is almost always some variation in the normal position, 

 shape, or other character, of the mine. Some species have dimorphic 

 mines, the difference between the two forms of mine being dependent upon 

 the difference existing between the leaves of the respective food-plants on 

 which the larvae may happen to find themselves feeding, and Wood 

 says that one species, X. mlicin, makes mines of three different forms, 

 its mine being condensed into a vermiform gallery in Sali.v aurita, 

 fairly straight in S. cajirea, whilst in S. alba and S. rmselliana the 

 mine becomes a blotch, the difference depending entirely on the 

 character of the leaf in which the mine is made. There is some 

 probability, as before suggested, that the mine in leaves of S. alba 

 is that of N. vimineticola. 



It would appear that in many species when the egg is laid on the 

 margin of a leaf (instead of more towards the centre) the normal 

 shape and character of the mine are altered, the mine in such cases 

 being spread out along the margin, and hence, it often happens that 

 two species, evidently closely allied in the larval and imaginal states, 

 will make very different-looking mines. It is clear that this is due to 

 the position in which the egg is laid, and hence a difference in the 

 shape of the mine need not betoken a want of affinity. 



Although Herrich-Schiiffer (Correspondenzblatt, ii., p. 174) was the 

 first to notice the moulting of the Nepticulid larva, Heinemann first 

 described the abnormal method in which the moulting was carried 

 out. He states that the larva is inactive for a time just before a moult 

 is to take place. The skin then cracks at the head, and the larva 

 proceeds to eat its way forward, because it can only, by eating a path 

 before it, obtain space to draw itself from its old skin. This, in the 

 confined space of the mine, gets drawn forward for a slight distance, 

 and is eventually lost to sight in the excremental track. He observed 

 the moulting in several species, and had remarked that it generally 

 took place at some part of the mine where the latter changed its 

 character, either from a slender gallery to a blotch, or from a spiral 

 mine to an irregular one, or from a very narrow gallery to a broader 

 one. Healy observed a larva of A r . aurella resting in the centre of its 

 mine on January 18th, 1868, " apparently in a sickly state. On the 

 following morning the skin split at the first segment, and the darkest 

 blotch at the back of the head had receded to the second segment. 

 On the 20th the old skin had shrunk to the fifth segment, and at this 

 date the whole of the first four segments had quite a transparent 

 appearance, being devoid of all markings whatever, and contrasting 

 strangely with the remainder of the body of the larva ; the larva lay quite 



