

[From the Transactions of the Linnean Society, vol. xxv.] 



I. On the Phenomena of Variation and Geographical Distribution as illustrated by the 

 Papilioniclae of the Malayan Region. By Alfred R. Wallace, Esq. 



(Plates I.-VIII.) 



Read March 17, 1864. 



When the natvu-alist studies the habits, the structure, or the affinities of animals, it 

 matters little to which group he especially devotes himself ; all alike offer him endless 

 materials for observation and research. But, for the piirpose of investigating the phe- 

 nomena of geographical distribution and of local or general variation, the several groups 

 differ greatly in their value and importance. Some have too limited a range, others are 

 not sufficiently varied in specific forms, wliile, what is of most importance, many groups 

 have not received that amount of attention over the whole region they inhabit, which 

 cotdd furnish materials sufficiently approaching to completeness to enable us to arrive at 

 any accurate conclusions as to the phenomena they present as a whole. It is in those 

 groups which are and have long been favourites with collectors that the student of dis- 

 tribution and variation will find his materials the most satisfactory, from their compara- 

 tive completeness. 



Preeminent among such groups are the diurnal Lepidoptera or Butterflies, whose ex- 

 treme beauty and endless diversity have led to their having been assiduously collected in 

 all parts of the world, and to the numerous species and varieties having been figured in 

 a series of magnificent works, from those of Cramer, the contemporary of Linnaeus, down 

 to the inimitable productions of owx own Hewitson. But, besides their abundance, their 

 universal distribution, and the great attention that has been paid to them, these insects 

 have other qualities that especially adapt them to elucidate the branches of inquiry already 

 alluded to. These are the immense development and peculiar structure of the wings, 

 which not only vary in form more than those of any other insects, but offer on both sur- 

 faces an endless variety of pattern, colouring, and textiu*e. The scales with which they 

 are more or less completely covered imitate the rich hues and delicate surfaces of satin 

 or of velvet, glitter with metallic lustre, or glow with the changeable tints of the opal. 

 This delicately painted surface acts as a register of the minutest differences of organiza- 



VOL. xxv. B 



qqb^H 



