DC 77//; GENESIS OF SPECIES. [Chap. 



also lliat tlic yKnoiis utouj) ol' rnjiilios never liave tails 

 ill tliL' ei^Uiitoiial ivgioiis ;iiul the Aiiiazuii valley, but 

 giiulually acquire tails in many cases as they range 

 towards the northern or soullicin tropic. Even in lMiro])e 

 we liavc somewhat similar tacts, for the species and 

 varieties of luitterllies peculiar to the Island of Sardinia 

 are f^enerally smaller and more d(»eply coloured than those 

 of the mainland, and the same has been recently sliown 

 to be the case with the connnon tortoiseshell butterllv in 

 the Tsl(^ of "Man ; wliih^ Papilio I/ospifon, peculiar to the 

 former island, has lost the tail, Avhieh is a i)rominent 

 feature of the closely allied P. Machaonr 



" Facts of a similai- nature to those now brought forward 

 would no doubt l)e found to occur in other groups of insects, 

 were local faunas carefully studied in relation to those of 

 the surrounding countries ; and they seem to indicate that 

 climate and other physical causes have, in some cases, a 

 very powciful etfect in modifying si)ecilic form and colour, 

 and thus directly aid in ]»rodncing the endless variety of 

 nature." 



AVith re<'ard to buttertlies of Celebes beloii'dntr to 

 dillereiit families, they present "a peculiarity of outline 

 which distinguishes them at a glance from those of any 

 other ])art of the world : " ^ it is that the U})i)er wings are 

 generally more elongated jind the anterior margin more 

 curved. ^loreover, tliere is, in most instances, near the 

 base an abrupt bend or elbow, which in some s])ecies is 

 very conspicuous. ^Ir. Wallace endeavours to explain 

 this phenomenon by the supposed presence at some time 

 of s]iecinl persecutors of the modifi(Ml fonns, supporting 

 the opinion by the remark that small, obscure, very 

 1 "Malay Archijiclngo," vol. i. i>. 439. 



