ON VARIATION IN COLOUR IN CERTAIN LARV.C 109 



their natural surroundings. I noticed this disposition espe- 

 cially in Catocala unpta and Bi.ston hirtaria, two larvae 

 which, in the newer squares of western London, occur 

 together, and are occasionally" found side by side on the 

 trunks of various species of poplar, willow, &c. On the 14th 

 of June 1 found six larvae of C. nupta on a small bough ol 

 willow : they were a little over a quarter of an inch in length, 

 of a pale brown colour, with no perceptible markings. These 

 1 put into a glass pan with their food and some old flannel, 

 as I had before noticed their fancy for resting on damp 

 pieces, which at one time I had wound round the stalks of 

 their food to keep it fresh : they are fond of lying close 

 against it, clasping it with all their legs, of which the first 

 two pairs are conspicuous liom their length, whilst the rest 

 are partly hidden by the curious fringe above them ; they 

 hide themselves in a fold of the flannel when about to moult. 

 These six larvae never gained in colour; their markings were 

 scarcely to be traced ; they remained very little darker than 

 the flannel during the whole of this stage of their existence. 



Alter I had had these larvae a short time I found another 

 on the same bough, quite different in appearance and 

 character, it was very dark, mottled with gray and black; 

 the cilia more conspicuous, probably owing to the dirt it had 

 collected in crawling about the bough. This larva had 

 recently moulted. 1 put it in with the others; and when in 

 time it went down into the flannel to change its skin I 

 watched for its reappearance with interest, wondering 

 whether confinement would modify the colour. Its new coat 

 was several shades paler than the skin it had cast ; and by 

 the time it was full fed its colour was exactly similar to the 

 others. 



In the early part of July 1 found several nearly full-fed 

 larvae on the trunks of trees — willow, Lombardy poplar, and 

 one on balsam poplar (possibly this last larva may have 

 crawled from a neighbouring willow, as it never touched the 

 leaves of balsam poplar with which it was supplied, preferring 

 the same fare as its companions). These larvae were close 

 against the tree, in little hollows in the bark ; when touched 

 they turned fiercely round, swinging their heads from side to 

 side, intimating very clearly ti)at they had a strong objection 

 to being touched, and that they meant to do battle lor their 

 liberty. When 1 had got them safely off' they continued to 

 wriggle, trying to start from my hand, as if they had some 

 dim consciousness of their future powers of flight. These, 



