442 BRITISH BUTTERFLIES. 



Lycsenid yet examined, differing in this direction markedly from 

 Rumicfa phlaeas and Heodes virgaureae (which are very similar to each 

 other). The slug-like aspect comes out in several ways. In the first 

 place, there are no dorsal ridges or flanges, which no doubt existed in 

 earlier instars, the whole dorsum being regularly rounded from the 

 margins all round. Secondly, the margins (marginal, or subspiracular, 

 flanges) are closely applied to the surface on which the larva is, and the 

 upper surface looks very flat, more so than it really is. In a large larva, 

 20mm. long, the width is 6mm., and the height 4-8mm. Thirdly, the 

 colour is very uniform, a vivid green. This varies, indeed, and even 

 the oblique lines can sometimes be supposed to be seen, but the lighter 

 yellower-green shadings are apparently buried deep in the tissues, and 

 the semitransparency of the larva generally adds to the slug-like 

 aspect. The minute hairs, which are very abundant, but invisible 

 without a lens, and the more conspicuous white dots (trumpet-hairs), 

 only accentuate the slug resemblance, giving an idea of slime, once 

 the slug idea is well-suggested. Further, in walking, the larva appears 

 to glide forwards slug-fashion, and it is only by close attention that 

 the slight vermiform (or caterpillar) movement passing along the 

 segments can be detected. The larva, however, if one can regard it 

 not as a slug, but as an emerald with a dewy coating, or simply as a 

 caterpillar, is really beautiful. The fullgrown larva, before it has 

 begun to get dull and shrunk for pupation, has a great thickness of 

 subcutaneous transparency, that makes any attempt to fix places for 

 the slight variation of tints it possesses almost hopeless, and, if done, 

 really misleading." According to Newman, the larva of the British form 

 was " f ullfed in June, and then lay flat on a dock-leaf, rarely moving 

 from place to place, and, when it did so, gliding with a slug-like motion, 

 the legs and claspers being entirely concealed." " The head," he says, " is 

 extremely small, and can be completely withdrawn into the prothorax. 

 The body has the dorsal surface convex, the ventral surface flat ; the 

 divisions of the segments are distinctly marked, the posterior margin 

 of each slightly overlapping the anterior margin of the next, and the 

 entire caterpillar having very much the appearance of a Chiton. The 

 sides are slightly dilated ; the legs and claspers are seated in closely 

 approximate pairs, nearly in a medioventral line. The colour is green, 

 scarcely distinguishable from that of the dock leaf ; there is an 

 obscure mediodorsal stripe, slightly darker than the disc, and in all 

 probability due to the presence of food in the alimentary canal." 

 Of the larval habits, Sich notes (in litt.) : " Newman was quite right 

 when he likened this larva to the marine animal known as a Chiton : 

 these creatures sit tightly pressed to the rocks, and nothing can be 

 seen of them but their backs, divided into so many segments. This is 

 just what the observer sees when looking at the larva? of C. dispar, as 

 they sit closely pressed against the surface of the leaves of Rumex 

 Jiydrolapathum. If irritated, the larva presses the lateral flange, which 

 is usually the low r est (or basal) portion of the larva visible, more 

 tightly against the leaf at the point irritated. If the irritation be 

 continued, the larva finally crawls quietly away, never attempting to 

 make any counter attack. As the larva is able to move its legs and 

 claspers without disturbing the dorsum, it seems rather to glide along 

 than to walk. As a matter of fact, it takes very short steps with a 

 continuous motion, and, as all the under-parts are very soft, their 

 movement does not affect any usually visible part of the larva, 



