IV DECREASE OF SIZE IN INSULAR FORMS 139 



in India, and South America, in closely related forms, instead 

 of light yellow, dark yellow, and greenish blue, then red and 

 blue and finally black appear. 



Influences of Locality on the Variation of Animals, and 



THEREBY ON THE FORMATION OF SpECIES 



Finally, on islands there are evidently some local external 

 influences of unknown nature, but probably likewise connected 

 with climate and nutrition, which control the evolution of 

 species, e.g. in butterflies, especially affecting tlieir size. 



I need only remind students of the Lepidoptera of the 

 Papilio-species of Java on one hand and of Celebes on the 

 other. The original identity of the species on the two islands is 

 obvious. But those of Celebes are now considerably larger 

 than their blood-relations in Java, and exhibit at the same time 

 slight differences of colour and marking more or less pro- 

 nounced when compared with the latter. To almost every 

 Java species there corresponds a larger, stronger species in 

 Celebes. This I have proved not merely from the material 

 already available in collections, but from numerous specimens 

 kindly collected for me by Herr Seubert, forest-overseer in 

 Java, and by Herr Bauer, merchant, in Celebes. 



The larger, more luxuriant island possesses, therefore, in this 

 case, the larger butterflies. Similarly the species of Papilionidae 

 which occur in the Antilles are smaller than those of the 

 neighbouring mainland, although otherwise but slightly 

 different from them. 



The butterflies of Sardinia also are in oeneral smaller and 



CD 



also more darkly coloured than those of the mainland. The 

 same holds for the common fox in the Isle of Man.^ It is well 

 known that Sardinia possesses numerous peculiar varieties, or 

 species of animals generally. Papilio Hospiton, which occurs 



^ A. R. Wallace, Beitrdge zur naturlichen Zuchtwahl, German edition, by A. 

 B. Mayer, 1870. 



