418 Mr. J. C. F. Fryer on 
of nature are usually the brown stems and trunks of the 
food-plant or neighbouring trees, while green pupae can 
only occur in shady positions, which are most often found in 
the midst of the fohage of the food-plant, where the twigs 
as well as the leaves are green. There will naturally be 
more errors among pupae which for protection should 
be green, as the slightest lack of shading, such as might be 
caused by the falling of a leaf, will cause the development 
of pigment. 
Since the above observations were made it has been 
possible to consult the literature * on the genus Papilio, 
though no case analogous to that of P. polytes has yet been 
found. Prof. Poulton in his extensive memoir + on the 
subject of pupal coloration recorded a few experiments on 
Papilio machaon, Linn., from which it seemed probable 
that the pupae of this species, though dimorphic, did not 
respond to the colour of their surroundings: in a later 
paper, t however, written in conjunction with Mr. Merrifield, 
he brings forward a number of fresh experiments and 
observations which tend to show that pupae of machaon 
can adapt their colour to that of their surroundings 
to a very considerable degree. This adaptation does not 
seem at all comparable with that of polytes, except in that 
darkness produced green pupae; in other respects machaon 
behaved more like such a species as Pieris brassicae. As 
a further point of interest it may be pointed out that winter 
pupae of machaon on reeds were in almost every case of 
the green form, a somewhat curious fact when it 1s remem- 
bered that reeds in winter, and in fact the predominant 
colour of a fen, are brown. 
Passing to observations on other species of Papilio, 
Fritz Miiller § records the pupae of Papilio polydamus, Linn., 
as being quite unresponsive to the colour of their sur- 
roundings. On the other hand, two Papilios in South 
Africa appear to behave more like Papilio machaon; the 
pupa of P. nireus, Linn., was shown by Mrs. Barber || 
to accommodate itself most accurately to the colour of 
its surroundings, and this observation was subsequently 
* My best thanks are due to Prof. Poulton, who most kindly 
read this paper and advised me on the subject of literature. 
y Phil. Trans. 1887, vol. 178, p. 406. 
+ Proc. Ent. Soc. 1898, Oct. 5, and Trans. Ent. Soe. 1899, p. 369. 
+ 
$ Phil. Trans. op. cit., quotation from Kosmos, vol. 12, p. 448. 
e) 
| Trans. Ent. Soe. 1874, p. 153. 
