278 THE entomologist's record. 



near relation of P. machaon, the ovum and larva are very similar, 

 though the female imago resembles P. troihif; more closelj'. P. philenor 

 is a subtropical butterfly, and more nearly allied to the Ornithoptera. 

 My results with these were, however, less conclusive. I found both 

 the green and red-brown forms of the pupa of P. pliilmor upon the 

 white wood of the butterfly-house, though the pupje on the young 

 stems of Loiiirera were of the green variety, and those on tree-stems, 

 etc., away from green leaves Avere red-broAvn. With regard to 7'. 

 asterias I found also that the pupse found upon the wood of the butter- 

 fly-house were indifferently green or brown, those on its foodplant, 

 fennel, were green. I removed, on August 6th, five larvae which had 

 already spun up for pupation upon the lowest black stems, and 

 pinned them up with as little of their former surroundings as possible 

 amongst the topmost green shoots, all five, however, changed 

 into brown pupae. At the same time I removed seven of the larvae 

 spun up amongst the green shoots, and pinned them to the black 

 stems at the bottom of the shrubs, taking care either to remove the 

 larvfp altogether from the brown stems to which they were attached, 

 or to change the colour of the latter by smearmg them with soot, etc. 

 All these, hoAvever, remained green, as did tAvo on stems Avhich I placed 

 indoors in a dark box. These larvae Avere removed from their natural 

 surroundings from tAvo to five days before pupation, indeed, as soon as 

 they Avere securely fixed up, a fact Avhich, I think, proA-es that Avhat- 

 ever determines the colour of the resultant pupa is an aft'air of some 

 time previous to the change itself. The above observations, in 

 addition to similar ones of previous years incline me to think that the 

 colour dimorphism of P. machaon is specially of a mechanical nature, 

 though, of course, the results are not conclusiAe. Amongst the yonng 

 stems of Lnnicera 1 found 20, the 14 green amongst the leaves or upon 

 the young Avood, with tAvo exceptions, Avhilst the six blacks Avere all 

 upon the lower skins of old wood. In addition to them I found a fcAV 

 pupae on London Pride, perennial phloxes, etc. Twenty-four larva", 

 Avhich I removed indoors and fed upon Sl,-iiiniiia in a large breeding- 

 cage of perforated zinc and wood, all changed to pup.e of the brown 

 variety. 



These results only confirm my observations of previous years, and 

 it appears to me that the presence of the more common green variety 

 is almost always coincident Avith pupation amongst green leaA'es. I 

 think it is certain that it is not due to exposure to more light, for all 

 the pupae Avhich I found in the full sunlight on the white-Avood of the 

 butterfly-house (some of these Avere even on the top) Avere of the 

 brown kind. To turn to another matter, r/c, the Avish to find out, if 

 possible, Avhen the colour of the pupa is determined. If, as I ha\'e 

 said before, the colour dimorphism of the /'. machaon pupae seems, on 

 the whole, to be of a mechanical nature, the instinct Avhich the insect 

 displays in its choice of an object on which to pupate is less easily 

 explained. As I have found over and over again, the individual larva 

 shows an extraordinary aptitude for never attaching itself either to the 

 trunk or branches of a tree Avith deciduous leaves, Avhere it Avould be 

 noticed by food-hunting birds during the Avinter (birds destroyed 800 

 P. machaon pupa? Avhich I had removed from their proper surroundings 

 and pinned up out-of-doors two Avinters ago), or the stem of a plant 

 Avhich would fall to the ground during the Avinter, and thereby cause 



