68 BRITISH BUTTERFLIES. 



machaon or P. alexanor may be when on a bare stem or other con- 

 spicuous point of vantage, in direct line with the human eye, yet, when 

 on the foodplant and among the foliage, a casual glance is rarely 

 sufficient to discover them, and if one wants them, one must prosecute 

 a close and prolonged search. Chapman has already noted (antea, 

 p. 64) that he fails to see the particular meed of protection gained 

 by the peculiar aspect of the young larva of Iphiclides podalirius 

 and, unless it be that which it apparently bears to a bird's 

 dropping, we cannot tell what 'it is meant to represent; Chapman 

 thinks that the larva is much too small in this stage for this to 

 be the real explanation in this case ; yet one supposes, since 

 the same general appearance is common to most young .Papilionid 

 larvae, that the value to the young larva is real, a view that is 

 strengthened by the fact that, in some species, this same appearance, 

 or a slightly modified form thereof, has been found effective almost 

 throughout life, no change of importance taking place in its general 

 appearance until the larvae are in their last or penultimate skin. This, 

 probably, is the answer to Chapman's objection, viz., that all the larvae 

 in the group did, atone time, keep this appearance throughout their larval 

 existence, as is the case now inHeraclide.s, and that this,what may be termed 

 generic, appearance has been, in some species, pushed back to the advan- 

 tage of special protective development, until, at last, the form is only found 

 in the first instar. In 1. podalirius, therefore, it now has, possibly, only a 

 shadow of its former value, and Bacot says (in litt.) that, "at Martigny, 

 in August, 1906, the young larvae in their first instar were especially 

 noticeable to human eyes, when search was made on a species of wild 

 cherry, but less so on blackthorn. He adds that he saw neither holes 

 nor spots on the leaves of the foodplant that could assist a cryptic 

 scheme, and that, in this instar, the larva was certainly as easy or more 

 easy to find than that of P. machaon in the same skin." The appear- 

 ance that makes certain butterfly larvae bear considerable resemblance 

 to a bird's dropping is not confined to Papilionid larvae, and Scudder 

 observes (op. cit., p. 1146) that " some butterfly larvae possess features 

 of a very surprising character, doubtless for the sake of protection 

 one of the commonest of which is the striking contrast between 

 creamy-white and black, or some other dark tint, which makes the 

 creature resemble the vermiform dropping of a bird. This is true of 

 all the American species of Baailarchia, of Polygonia faunus, and, 

 especially in their middle stages, of several Papilionid larvae, such as 

 those of Euphoeades troilus and Heraclides cresplwntes." It is equally 

 true of the larva of Polygonia c-album and the young larva of Papilio 

 machaon in Britain, and the peculiar position usually taken up on the 

 stem or petiole of the foodplant by the larva of the latter, and the 

 peculiar coiled position of rest in the middle of a leaf adopted by the 

 former, give additional point to the suggested resemblance. 



Little is really known about the larvae of the huge mass of tropical 

 Papilionid species ; but the studies of Edwards and Scudder have given 

 us some important facts about the North American species to add to 

 those already known concerning the European species. Scudder gives 

 a brief review of the changes that the larvae of the former undergo in 

 his Butts. New England, pp. 1234-1241, and thus summarises his facts 

 (p. 1238) : " There is a somewhat general uniformity of type in the 

 earliest stage of larval life among the Papilionines, whilst there is an 



