124 



NATURE 



[October 9, 19 19 



rete group of the genus ; while the red costal streak 

 suggests the influence of a representative in Bali of the 

 belisama group, lilce D. splcndida and D. oraia in the 

 other islands. 



Finally, in the island of Sumba we have another 

 member of this remarkable group of Huphinas. 

 Huphiiia Julia, the butterfly referred to, so closely 

 resembles Delias fasciata of the same island, that even 

 the sceptical Fruhstorfer is constrained to speak of it 

 as a "faithful copy" of that insect. But here once 

 more it is noticeable that one of the most conspicuous 

 features of the Huphina is absent from the Delias. 

 This time it is not, as in the case of /). splendida, the 

 submarginal row of scarlet spots on the underside of 

 the hindwing, but it is the scarlet costal streak that is 

 wanting. Huphina julia was discovered by Mr. 

 Doherty in the year 1887, and described in 1891. It is 

 interesting, in the light of what is now known of the 

 butterfly fauna of the Lesser Sunda islands, to read 

 what Doherty has to say about the mimicry question in 

 relation to the Delias and Huphina forms that have 

 just been mentioned. Speaking of H. julia, he says, 

 "If it stood alone, I should certainly suppose it to be 

 a mimic of some form of Delias hyparete yet undis- 

 covered in the island. But both H. laeta and H. 

 temena require to be accounted for in the same way, 

 and while it is possible that some Timorese Delias may 

 resemble H. laeta, I feel sure that H. temena can have 

 no such original. It must then be assumed that this 

 •group is less pressed by its enemies in the Timorian 

 Islands, and has therefore been able to acquire more 

 brilliant colours than its allies." So far Doherty. 



Whatever may be the value of this last hypothesis, 

 -we have just seen that the sup]X)sed facts on which 

 it rests are non-existent, for (i) the "form of Delias 

 hyparete as yet undiscovered " has actually turned up 

 in the person of D. fasciata ; (2) it is not only possible, 

 but actually the case, that "some Timorese Delias may 

 resemble H. laeta"; (3) Mr. Doherty "feels sure that 

 H. temena can have no such original," but Delias 

 ^raia and Delias swmbawana have just the same rela- 

 tion to Huphina temena ^s D. splendida and D. 

 dohertyi to H. laeta. In view of these facts it may be 

 not rash to suppose that the apparent absence of a 

 model for the red costal streak of H. julia may here- 

 after be accounted for. 



Of the three instances of possible mimetic association 

 which have now been mentioned, I think that only 

 one, viz. the first, has previously been treated in 

 detail. The numbers of cases more or less similar to 

 these three might be very largely extended, but for 

 our present purpose it will be sufficient to confine our 

 attention to those already given. It is probable that to 

 some minds the facts adduced are simplv curious coin- 

 cidences, needing no explanation ; but it can scarcely 

 be wrong to suppose that to most students of nature 

 the observed phenomena do call for some attempt at 

 interpretation ; and on a review of the evidence it 

 seems clear that the geographical element must enter 

 largelv into any explanation that may be offered. On 

 the whole, it is certainly the case that the forms which 

 are supposed to be related by mimicry do inhabit the 

 same localities; the continental Prioneris, for example, 

 is like the continental Delias, and the island Prioneris 

 recalls the island, not the continental, Delias. More- 

 over, we find the differences between the Delias of 

 Timor, of Sumbawa and Sumba reflected in the asso- 

 ciated Huphinas of the same islands. If it be granted 

 that the gfographical element is a factor, it is natural 

 10 inauire how it works. 



It is no doubt true that external geographical con- 

 ditions are occasionally capable of producing, whether 

 directly or indirectly, a community of aspect in the 

 animals or plants exposed to their influence. The pre- 



NO. 2606, VOL. 104] 



valence of a sandy coloration in the mammals and 

 birds of a desert, and of whiteness in the inhabitants 

 of the arctic snow-fields, the spiny character so often 

 assumed by the plants of arid regions, and the general 

 dwarfing of the vegetation that grows close to the 

 sea, may be given in illustration. At first sight these 

 phenomena may seem to be of the nature of direct 

 effects of the environment; quite possibly some of 

 them are so, but I think few observers would denv 

 that they are at least largely adaptive, being used 

 for purposes of aggression or defence. Still, even if 

 we allow the direct effect of the environment, as per- 

 haps we may do especially in the case of the plants, 

 can we frame any hypothesis of the action of geo- 

 graphical conditions which shall lead directly to the 

 assumption of a common pattern in the case of the 

 three or four butterflies from New Guinea ? I confess 

 that I am quite unable to do so. If the climate, or the 

 soil, or any other geographical condition in New 

 Guinea is capable of directly inducing so remarkable a 

 combination of colour as we see in these Pierines and 

 Nymjihalines, why does it not affect other organisms 

 in a similar way? Why do not other Pierines, for 

 instance, closely related to ornytion and abnormis, 

 share in the same coloration? And considering the 

 characteristic aspect of the underside, which is sup- 

 posed to be called into being by some unexplained con- 

 dition peculiar to New Guinea, we may well ask. Why 

 should its most conspicuous features belong in the one 

 case to the forewing and in the other to the hindwing, 

 and vice versa, the general effect being the same? 



Fruhstorfer, we may note, does not feel these diffi- 

 culties. "Many Pierids," he says, "present typical 

 examples of that resemblance to other butterflies which 

 has been named mimicry. The origin of this resem- 

 blance, however, is now explained by the supposition 

 that the mimics were modified by the same (as yet 

 unknown) influences under which the colouring of the 

 models, mostly Danaids, developed." I think it will 

 be generally agreed that this reference to "unknown 

 influences " is no explanation at all. 



It is necessary to take into account the fact that the 

 resemblances of which we are speaking are independent 

 of structural differences, being, in fact, merely super- 

 ficial. This is a jxjint which is capable of much wider 

 demonstration than I am giving it to-day. But even 

 from the instances now before us 1 think there cann<>t 

 be much difficulty in coming to the conclusion that 

 the resemblances are an appeal to vision. They are 

 meant to be seen, though by whom and for what 

 purpose may be op<Mi to question. Speculations as to 

 recognition and sexual attraction may, I think, in 

 these cases be put out of court; but there remains 

 the theorv of warning colours assumed in reference to 

 the attacks of vertebrate enemies. From the fact 

 that the most striking and most conspicuous of these 

 common aposemes or danger-signals belong to the 

 under surface — that is to say, the part chiefly exposed 

 to view during rest — it may be inferred that the enemies 

 to be guarded against are mainly those that attack 

 butterflies, not on the wing, but when settled in repose. 

 Both birds and monkevs are known to feed on butter- 

 flies, and there is a good deal of evidence as to their 

 preference for one kind of food over another. I will 

 not stop to give details, but anyone who wishes to 

 study the evidence mav be referred especially to the 

 memoirs of Dr. G. A.' K. Marshall, Mr. C. F. M. 

 Swvnnerton, and Capt. G. D. H. Carpenter. 



If the warning-colour interpretation of these resem- 

 blances be the true one, we see at once why thev are 

 so largely independent of structure and affinity. Being 

 meant to catch the eye, they ride rough-shod, so to 

 speak, over inconspicuous features, such as venation; 

 nor do they respect more than the nature of things 



