to an Insect Fauna of the Amazon Valley. 353 



the supposition of any considerable amount of extinction. The 

 fauna of the Guiano-Amazonian region, as far as regards this 

 genus, is in the highest degree peculiar; showing no dependence 

 on that of the countries near either of the tropics. If now we 

 except the local varieties (the inclusion of which would only 

 strengthen the position), there are about forty perfectly distinct 

 species of this genus inhabiting this region, and of these no less 

 than eighteen * are endemic, all of them so peculiarly restricted 

 in their range, that they are not found, nor any forms closely 

 representing them, even at twelve degrees of latitude on either 

 side the equator. The result is plain, that there has always (at 

 least throughout immense Geological epochs) been an Equatorial 

 fauna rich in endemic species, and that extinction cannot have 

 prevailed to any extent within a period of time so comparatively 

 modern as the Glacial epoch in Geology. 



Before dismissing the genus Papilio, I think it will be con- 

 sidered a service rendered to future students if I add a list of all 

 the published species of the most difficult group of the genus, 

 viz., that oi j^neas and its allies, with the chief synonymy j my 

 endeavours to understand the Amazonian species having led me 

 to make considerable research into the literature and natural his- 

 . tory of the whole of the American species. As in all dominant 

 groups; i.e. groups which seem adapted under the present con- 

 ditions of existence to increase and spread; the separation into 

 species is extremely difficult. I have found it impossible to 

 bring forms, which have so many different grades of relationship 

 to their next of kin, into a series of well-defined species. I have 

 endeavoured, therefore, to read nature as I have found her, and to 

 arrange the forms according to the amount of difference between 

 them respectively ; having regard always to the important point, 

 whether the difference be constant or not amongst the individuals 

 concerned. Thus, differences in one or a iew individuals in a 

 locality where the typical form prevails, I have treated as simple 

 varieties ; others of more importance, either through the increased 

 amount of difference and the tendency to occur only in certain 

 localities, or through prevailing amongst all the individuals in a 

 locality to the exclusion of the. type, I have considered as local 

 varieties or sub-species. The next grade of forms, that in which 



* Lycidas. Coristeus. Hippason. Panthonus. Eurhteus. Orellana. Ver- 

 tumnus. Mneas. Eigetelei. Bolivar. jEiieidei. Echelus. Lysander. Aglaope. 

 Triopas, Chabrias. Ariaralhes. Columbus. 



