86 ON SOME LEPIDOPTEEOUS LATIVtE. 



have an olive-green ground colour, instead of the rich 

 purple-brown which generally prevails ; but as this colour 

 rarely persists into the last stage of the larva, being usually 

 discarded for the brown hue in change of skin when the 

 larva is about half-grown, the green variety is probably 

 the survival of an older coloration now abandoned by the 

 majority of the individuals of the species. Each form bears 

 the longitudinal yellow stripe, and both feed quite exposed 

 and on the upper side of the leaves of broom or bracken, 

 and are evidently distasteful. And this change of colour 

 of a larva when partially grown leads me to speak of the 

 strange change of coloration and habit undergone by the 

 caterpillar of Acronycta alni, a moth rather rare in Eng- 

 land, but one of the most interesting species to rear which 

 has ever come under my notice. The larva feeds on lime, 

 alder, and other trees, and during the greater part of its 

 life is most sluggish, nearly always resting on the uppefr 

 side of a leaf with its head bent round touching its side, 

 eating a hole in the middle of the leaf, and being scarcely 

 ever seen in motion. In this peculiar position, with its soft 

 grey and black colouring, it very much resembles excreta 

 dropped by a bird ; and to this, no doubt, owes much of its 

 protection, though a close inspection reveals several long 

 hairs with spatulate points, no doubt a warning to any too 

 curious bird to beware of tasting. But at the last skin- 

 change a remarkable metamorphosis occurs — the larva puts 

 on a garb of intense blue-black, with striking yellow 

 patches on the upper side of each segment : the broadly 

 pointed and flattened hairs are still more conspicuous, 

 and the caterpillar appears in full perfection of warning 

 colours. It also at the same time develops a complete 

 change in its habits, and crawls (I had almost said runs) 

 with quite a rapid motion over the foliage. It probably 



