530 MR. H. W. BATES ON THE LEPIDOPTERA 



further to the west, the species was again extremely variable, but the varieties were 

 quite different from those of Ega : individuals coming very the near type occurred, but 

 not one was found quite conformable. M. Ugaensis was quite absent ; but, on the other 

 hand, a new variety abounded at St. Paulo, of which there was certainly no trace at 

 Ega ; this has been figured and described as a distinct species, viz. M. Mazceus (Hewits. 

 Esot. Butt. Mechanitis, fig. 8). Two other remarkable varieties also occurred — one near 

 31. MenopJdlus (Hewits. I. c. Mechanitis, figs. 2, 3), and the other with a structural 

 modification in the shape of the wings, described below as M. Olivencia. 



The way in which I found this species to vary, as just described, impressed me greatly, 

 and helped much, in conjunction with other facts of a similar tendency, not only to 

 destroy my belief in the constancy of species, but to teach how new ones may have 

 originated. The complete set of connecting forms found showed that I had here to deal 

 with one species only, disseminated over a large area, and modified in certain districts 

 under pecixliar conditions there obtaining. The varieties were of such a nature as to 

 form and colours, that it was inconceivable they could have been hybrids produced by 

 the intercrossing of two or more originally distinct species. The amount of local 

 modification exhibited was not in accordance with obvious differences in the local 

 conditions ; for the species Avas totally changed from Ega to St. Paulo, 260 miles apart 

 and very similar in soil, climate, &c., whilst very constant on the Lower Amazons, in 

 districts 600 miles apart and very different in physical conditions. Since returning 

 to England, I have learned that M. Folymnia again varies on the eastern slopes of the 

 Andes, whilst a cluster of remarkable varieties or local forms (some of which have been 

 described as species) are found in the Andean valleys. Some of these {M. Macriuns, 

 M. MenopMltis, &c.) are very clearly varieties of M. Folymnia, like the forms found at 

 Ega and St. Paulo ; but others {M. Mothone, M. Menapis) are more sharply defined, and 

 have the appearance of true species. Now I think the conclusion is unavoidable, that 

 these apparently distinct species are modifications, as well as the undoubted varieties are ; 

 for we have the species in all stages of modification — simple variation, local variety 

 scarcely distinguishable from a mere variation, complete local variety, and well-marked 

 race or species. The forms of M. Folymnia found in South Brazil confirm this view. 

 At Rio Janeiro the well-marked race or species Jf. Lysimnia alone is found ; at Bahia 

 (travelling towards the home of the type, M. Folymnia), M. Lysimnia in company with 

 M. Nescea, a form exactly intermediate between M. Folymnia and M. Lysimnia; at 

 Pernambuco (further northward) 3L Nescea alone occurs ; at Para this form is seen no 

 more, and M. Folymnia in its typical dress monopolizes the field. 



These facts seem to teach that, in this and similar cases, a new species originates in a 

 local variety, formed in a certain area, where the conditions are more favourable to it 

 than to the typical form, and that a large number of such are simultaneously in process 

 of formation from one variable and widely distributed species. The new species cannot 

 be proved to be established as such, unless it be found in company with a sister form 

 which has had a similar origin, and maintaining itself perfectly distinct from it. Cases 

 of two extreme varieties of a species being thus brought into contact by redistribution 

 or migration, and not amalgamating, will be found to be numerous when the subject is 



