48 Mr. E. B. Poulton's notes upon the colours 



in any position except one. This one position is the 

 median ventral line, and this was the only other place 

 where mature fat-cells could be found. Here they were 

 collected round the ventral gangliated nerve-chain, and 

 formed the white ventral line. In this position they are, 

 of course, completely invisible in all natural positions 

 of the larva. 



Cells partially filled with fat are very common in other 

 parts of the body, but none of these appeared white by 

 reflected light, and I have no doul)t that such cells are 

 only found along the dorsal and ventral line. This was 

 certainly the case in the specimen I dissected, which 

 was probably full-grown, as I had noticed some slight 

 changes of colour indicating the nearness of pupation. 

 The spiracular line is merely the result of an extremely 

 transparent skin important in producing other markings, 

 and the former is thus incidental to the latter. It seems 

 very probable that in many other cases also natural 

 selection has taken advantage of the ready-formed 

 colours of internal organs to produce the markings of 

 larvae. Indeed, the effect of the dorsal vessel in this 

 direction, and the intensification of a general green 

 colour from internal causes, are already well known in 

 many lepidopterous larvae. I was able to name the 

 hymeno]3terous larva described above from Cameron's 

 monograph on the British phytophagous Hymenoptera 

 (Eay Society, 1882). Mr. Cameron draws attention to 

 the attitude of the larva at rest, when it clings close to 

 the curved surface which it has eaten out of the leaf. 



Two KINDS OF PROTECTION BY RESEMBLANCE TO SURROUND- 

 INGS, SPECIAL AND GENERAL. — In the wcll-kuown cases of 

 protective mimicry the organism resembles more or less 

 exactly some portion of its environment. Thus the 

 larva of S. ocellatus is protected by resembling the under 

 side of a curled apple leaf (when it feeds on this plant). 

 Holding the larva in one hand and the twig in the other 

 the resemblance is marked, and the observer is led to 

 wonder at the protection afforded. This is special pro- 

 tective mimicry, and to the same class belong the number- 

 less beautiful instances of protection familiar to us from 

 our own observation or that of others. But there is 

 another kind of protective resemblance to which less 

 attention has been directed, which is less apparent 

 although not less real. Holding the larva of Sphinx 



