734 TRANSACTIONS OF SECTION D. 



only in the theoretical stage; it was never developed by him, and although he 

 mentioned a few instances in support of his view, he did not attempt to trace the 

 supposed mutually mimetic process in any detail. There is, nevertheless, much 

 evidence that such reciprocal approach, or interchange of obvious characters, does 

 actually occur ; and some cases of mimicry are here exhibited, the peculiar features 

 of which are difficult to explain on any other hypothesis. 



Thus the resemblance between Leuceronia pharis, Boisd., and the form of 

 Nychitona medusa, Cram., which inhabits the same districts of Central Africa, 

 appears to be due to mutual assimilation, the Leuceronia having borrowed its 

 peculiar outline and the attenuation of the dark apical patch from the Nychitona, 

 while the wings of the latter form owe their spotlessness and the comparative 

 opacity of their white pigment, in both of which respects they differ from the 

 forms nearest to them by affinity, to imitation of the Leucero7na. 



Similarly, the mimetic relation between Heliconius as represented \>y H.guaricus, 

 Reak., or H. haenschi, St. and Riff., and certain Pierines or ' white ' butterflies 

 such as Pereute leucodrosime, KolL, and Pieris lociista, Feld, may very possibly be 

 due to an interchange of certain features between them. 



Again, there is in the Island of Bali a certain Pierine butterfly, Ixias baliensis, 

 Fruhst., the female of wliich presents a general resemblance to another Pierine, 

 Hvphina cori'a, Wallace, found in the same island. In view of the usual aspect of 

 the nearest allies of these two forms respectively, the conclusion suggests itself 

 that the Ixias has assimilated its forewing to that of the Huphina, and the 

 Huphina its hind wing to that of the Ixias. 



The females of certain Central and South American Papilios, or,' Swallow-tails ' 

 (as P. iphidamas, Fabr., P. nephalion, Gudt., &c.) are in close mimetic relation 

 with both sexes of some common species of the Pierine genus Euterpe' (e.g., 

 E. approximata, Butl., E. tereas, Godt., &c.) The suggestion is offered that 

 although in most respects the Papilio has plainly influenced the Pierine, it is yet 

 due to the influence of the latter that the females of the former have not adopted 

 more closely the aspect of their own males. 



For this phenomenon of mutual approach, or reciprocal influence, the term 

 Diaposematism has been proposed by Professor Poulton. The possibility of its 

 occurrence has been questioned on a priori grounds, but, it would appear, without 

 sufficient reason. 



6. (i) Mimicry in the Butterflies of North America, (ii) Recent Investi- 

 gations iipon the African Swallow-tail Butterfly Papilio dardanus 

 (meropc ) as an Example of Mimicry. By Professor E. B. Poulton, 

 F.li.S. 



7. Some of the chief Mimetic Combinations amx)ng South American 

 Butterflies, By J. C. Moulton. 



FRIDAY, SEPTEMBER 4. 



The following Papers and Reports were read : — 



1. An Inquiry into the Feeding Habits of British Birds. 

 By C. Gordon Hewitt, M.Sc. 



It is becoming increasingly difficult, with the introduction of scientific methods 

 into agriculture, horticulture, and forestry, for zoologists studying economic 

 problems to form a definite opinion with regard to the economic status of many 

 species of the birds of our islands, such as, for example, the rook, jay, starling, 

 chaffinch and other finches, and many other birds. 



