178 THE MALAYAN PAPILIONIDJE AS 



exceed in size those of Gilolo and New Guinea why 

 the tailed species of India should begin to lose that 

 appendage in the islands, and retain no trace of it on 

 the borders of the Pacific, and why, in three separate 

 cases, the females of Amboyna species should be less 

 gaily attired than the corresponding females of the 

 surrounding islands, are questions which we cannot 

 at present attempt to answer. That they depend, how- 

 ever, on some general principle is certain, because ana- 

 logous facts have been observed in other parts of the 

 world. Mr. Bates informs me that, in three distinct 

 groups, Papilios which on the Upper Amazon and in 

 most other parts of South America have spotless upper 

 wings obtain pale or white spots at Para and on the 

 Lower Amazon ; and also that the ^Eneas-group of Pa- 

 pilios never have tails in the equatorial regions and the 

 Amazons valley, but gradually acquire tails in many 

 cases as they range towards the northern or southern 

 tropic. Even in Europe we have somewhat similar 

 facts ; for the species and varieties of butterflies peculiar 

 to the island of Sardinia are generally smaller and more 

 deeply coloured than those of the mainland, and the 

 same has recently been shown to be the case with the 

 common tortoiseshell butterfly in the Isle of Man ; 

 while Papilio Hospiton, peculiar to the former island, 

 has lost the tail, which is a prominent feature of the 

 closely allied P. Machaon. 



Facts of a similar nature to those now brought for- 

 ward would no doubt be found to occur in other 

 groups of insects, were local faunas carefully studied in 



