THE NEfTICULfDES. 169 



on the upper surface of the smooth-leaved S. alba, and on the under- 

 surface of the rough-leaved S. cinerea and S. caprea, the reason sug- 

 gested by Wood being that, on the latter plants, although the leaves 

 are clothed below with a woolly covering, the hairs stand on end, and 

 the moth is able to push her ovipositor between and reach a firm base ; 

 whereas, in the former, the covering is not only extremely dense, but 

 is also brushed close down upon the surface, so that the upper side, 

 where the hairs are not so thick, is selected instead. It has been sug- 

 gested to us by Fletcher, that the species on SalLr alba is N. mmineti- 

 cola, which not only differs in its mode of egg-laying, but also in its 

 cocoon, etc., from A T . salicis, which is the species found on SalLv 

 cinerea and S. caprea. 



The adult larva is flattened, with a very small pointed head, 

 notched deeply behind. The head is almost buried in the tumid and 

 projecting prothorax, which is wide, but less so than the mesothorax. 

 The width of the latter is maintained somewhat uniformly to the 7th 

 abdominal segment, the hinder ones diminishing rapidly, the 9th and 

 10th abdominal segments being very small and somewhat telescoped. 

 The legs, as already noticed, are remarkable, having the usual proleg 

 structure, but being without booklets. They are also much more 

 prominently developed in some species than others. Wood says that 

 there are no legs on the prothorax, large ones on the meso- and 

 inetathorax, none on the 1st, but present on the 2nd to the 7th 

 abdominal segments eight pairs in all. De Geer states that " the 

 larva (of N. anomalella) has eighteen legs, all similar in form, all mem- 

 branous, fleshy and destitute of hooks, without any ordinary true legs. 

 The legs are all similar to those of the larvae of sawflies, pyramidal 

 or conical in shape. A pair is placed on each of the nine segments 

 which follow the first, the first, eleventh and twelfth body segments 

 being devoid of legs." De Geer further states that the larvae can 

 walk on all kinds of surfaces, the whole body and legs being covered 

 with a sticky or viscous matter which retains them on the objects 

 upon which they walk. Some larvae (e.;/., that of N. septembrella) 

 appear to have no legs. The segments of the larva are distinctly 

 separated by a deep incision, with a round (rather than oval) section, 

 whilst the meso- and metathoracic segments are somewhat square in 

 outline. The transparency of the dermis and the tissues generally, 

 allow some of the internal organs to come into view. 



The most important larval characters that have been used for the 

 discrimination of the various species are as follows : (1) The general 

 colour of the body. (2) The colour of the head. (3) The markings 

 on the prothorax. (4) The medio-ventral chain of marks extending 

 down the abdomen. (5) The colour of the intestinal canal. (61 A 

 pair of dark lines on the dorsum of the 7th, 8th and 9th abdominal 

 segments. 



The larval ground-colour varies, according to the species, from 

 greenish-white to bluish-green, the intermediate tints of some shade 

 of yellow and green being the most common. There is occasionally 

 some fading of tint as a larva reaches maturity (and this probably 

 explains apparent discrepancies in different descriptions of larvae of the 

 same species). The head varies from pale grey to black, pale brown 

 or an amber tint, being, perhaps, the most common, but the ground- 

 colour of the larvae of the same species varies but little, hence it becomes 



