PROTECTIVE COLORATION AND DEFENSIVE STRUCTURES OF LARVAE. 88 



curiously coloured circles on the back of the abdominal segments 3 

 and 5, which are more brilliant with their blue and yellow than any- 

 thing on an Arbutus leaf, nevertheless produce exactly the effect of 

 certain little rings of fungus or decay, that are very common on the 

 leaves. 



In the mimicry of larvae, then, it is to be noticed that many of 

 them do not so often exactly imitate the thing mimicked, as some 

 particular aspect of it under certain illuminations, and so, in <?. jasius, 

 the larva is not at all like a leaf, but many leaves on a tree will look 

 exactly like some particular larva does as it rests amongst them. In 

 the same way, the head does not resemble the buds at all closely, yet, 

 Chapman says, he has fancied he saw a larval head, when, after all, 

 it was only a group of buds. 



Perhaps the most typical instance of this indirect mimicry is 

 exhibited by the larva of Acronicta leporina, which, seated beneath an 

 alder leaf, looks exactly as if a spot of sunshine were falling upon the 

 upper side of the leaf. This larva, considered away from its food- 

 plant, is very conspicuous. It is dimorphic in its coloration, one 

 form of the larva beipg green with white hairs (attached more par- 

 ticularly to alder), the second yellow, with distinct chocolate dorsal 

 and lateral bands, olive-brown beneath, with yellow hairs (attached 

 more particularly to birch). Chapman has observed that the white- 

 haired form sits somewhat curled round, near the middle of the 

 underside of an alder leaf. Looking down from above it is absolutely 

 hidden, looking up from beneath it ought to be very evident, but 

 this is far from being the case. Chapman says that he has several 

 times missed a larva till he has looked three or four times, and has 

 also fancied he saw a larva where none has been. In looking up from 

 below through the foliage of an alder tree, most of the lower leaves 

 are in the shade of the upper ones, but here and there a gleam of light 

 falls through upon a portion of a leaf, and gives it quite a different tone 

 and appearance as seen from beneath. A larva of A. leporina, seated 

 beneath an unilluminated leaf, precisely resembles one of these patches. 

 Poulton considers that the yellow larva on birch is protected by its 

 resemblance to a cocoon, but Chapman points out that cocoons are not 

 very common objects on birch leaves, although, as he shows, the deserted 

 domiciles of larvae, such as Asphalia jlavicomis, etc., are so, and the 

 resemblance of the larva to these is heightened by the black tufts that 

 often persist in the yellow form, and which resemble bits of frassand dark 

 chips that are frequently entangled in such vacated lodgings. At any 

 rate, A. leporina presents a marked instance of a dimorphic larva, each 

 form being suited to different circumstances, and almost certainly for 

 purposes of concealment. Freer has pointed out that on Cannock 

 Chase, where both forms occur, the green one being confined to alder, 

 the yellow form is the later one, and, occurring principally on birch, 

 is of the same tint as the dying birch leaves. 



Dyar, commenting on the mimicry exhibited by the larvae of the 

 American Acronyctids, says (Trans. New York Acad. <Sci.,xiv., p. 58) : 

 The larvae of the genus Acronycta (in its wider sense) are wonderfully 

 varied in appearance, and I believe that this diversity is due to 

 mimicry of all sorts of objects, from that of resemblance to the foliage 

 (i/rixi'a, tritona, etc.) to warning colours (oblinata), and mimicry of 

 special objects, such as a spider's nest (culpina), or of some other 



