POLYMORPHISM AND DIAGNOSIS 71 



of a specimen. Similarly when it is traced southward 

 in Africa, dorippus is dominant in the coast strip of 

 British East Africa, where it constitutes about three- 

 quarters of the total number of individuals. Further to 

 the south it becomes rarer and rarer, until in Natal and 

 the Cape, if it occurs at all, it is even rarer than in Ceylon. 1 

 Such a distribution is consistent with the interpretation 

 that dorippus and chrysippus are two forms in one syn- 

 gamic community. It is difficult on any other hypothesis 

 to account for the facts which we observe on the out- 

 skirts of the range of dorippus the occasional appearance 

 of single individuals in the swarms of the type form. 

 And if the two are syngamic on the outskirts, the gradual 

 transition in proportions towards the metropolis of dorippus 

 suggests that they are syngamic throughout. Common 

 as the species is probably the commonest butterfly in 

 the world the evidence from Epigony has never been 

 obtained, although from the point of view of heredity the 

 investigation promises to be of the deepest interest. 



The remarkable forms of the females of the Papilio 

 dardanus (merope) group already alluded to afford another 



Of five or six more recent examples Major Manders writes, ' These speci- 

 mens were captured by Mr. Pole at Puttalam on the east coast and 

 Hambantotte on the south coast in the dryest and perhaps most arid 

 portion of the island. It is evidently widely distributed in the desert 

 portion of the island and is possibly not uncommon.' 



' The distribution of this insect in India cannot yet be fully known ; 

 it is rare in Canara, but is not yet reported from the plains of the Deccan, 

 or Southern India so far as I am aware though it probably exists.' The 

 occurrence of dorippus at Bombay, Khandalla, Poona, and Karachi had 

 been previously published by Col. C. Swinhoe (P. Z. S. 1884, p. 504; 1885, 

 p. 126) ; and at Campbellpore (Col. Yerbury) by Dr. A. G. Butler (P. Z. S. 

 1886, p. 356). 



1 Mr. Roland Trimen tells me that he knows of only three South 

 African dorippus : two from Durban and one from Pretoria. The latter 

 and one of the former were taken by Mr. W. L. Distant (Ann. Mag. Nat. 

 Hist. (7), vol. i, 1898, pp. 48, 49). Mr. Geo. F. Leigh, of Durban, 

 Natal, writes March 3, 1904: 'I have myself captured two or three 

 specimens during the past three years, and one was taken only last 

 September by Mr. Burn who was out collecting with me.' Two speci- 

 mens captured in 1905 at Salisbury, Rhodesia, have been presented to 

 the Oxford University Collection by Mr. Guy A. K. Marshall. They 

 are, so far as I am aware, the only examples of dorippus hitherto recorded 

 from Rhodesia. 



