INTKUDLiCTiUN. By Dr. A. yEii/. 5 



Aristolochia-Papilios whicli occur there — e. g. in South Brazil as P. pompoiiiiit^, mimicking P. pvi-rhrlms, in 

 Rio de Janeiro in tlie form h/nilbo/is, cojiying P. (if/nrug — yet vvitliout doubt sucli cases are wanting in 

 America as that of the Indian /'. iiieiinion. in wliich some 30 ditferent forms of female belong to one almost 

 constant male form. 



The strict localisation of Lepidoptera in America is easily explained by the peculiarities of the 

 conditions of vegetation. Like the Old World steppes, the prairies of North America and the Pampas of 

 South America are not adapted to produce a great abundance of forms or even a inoderate number of 

 showy and elegant species. Hence we find Morpho, the larger Nymphalids, Cus/iild , etc., disappear rather 

 suddenly from the district as soon as we leave the great Southern and Central American forest region. Hence, 

 also, the West Indies, which are either poor in forests or altogether devoid of them, are far behind the 

 neighbouring mainland in respect of their le})idopterous fauna, while conversely the East Indian Archipelago 

 is especially rich in species. 



It greatly surprises those who \isil ditferent jtarts of the American continent to notice the great 

 resemblance between northern and southern districts which are separated by vast tracts of land differing 

 entirely from both. The Argentine jiampas produce species altogether analogous to those of the United 

 States, often even the same species, while they are absent from the whole of the Neotropical forest region 

 which intervenes. Almost at the same latitude where the last Morpho leaves us, whether northward or 

 southward, we find CoUaa, Pi/raniris fanjc and Dciojiein tlying. Kiiploirhi cldndin occurs both in the United 

 States and in Uruguay in hardly distinguishable forms, wliile in the intervening tropical South America it is 

 entirely absent, being supplanted by the very ditferent Enjit. hcfpsid. Nothing analogous is known in the 

 Eastern Hemisphere : the lunnerous Acraeas of South Africa vanish in the tropical zone and do not reappear 

 north of the Sahara: Ar<i//Hii/s, which in America appears again in Chili and Argentina after missing the 

 tropics, vanishes finally in the East on reaching the tropical I'egion; neither South Africa nor Australia 

 possesses any species of the Nymphalid group, which is so plentifully rejiresented in the North. On the 

 contrary the well-represented Precis;, Amaiirk, etc., of South Africa do not reapi)ear in North Africa or in 

 Europe, and of other characteristic genera of the Old World, such as Tcmrohis and <'h(iraxe:<, scarcely one 

 species in a hundred extends from one temperate zone across the tropics to the other. 



The role which the individual families play in the American fauna will be easily seen from the 

 special part; attention need only he called here to a few points which result from a comparison of the 

 fauna of the New W^orld with that of the Old. 



The Papilios of temperate North America surjiass those of the corresponding latitudes of the Old 

 World. San Francisco, St. Louis or Washington has two or three times as many species of PapiJio as 

 Spain, Algiers or Asia Jlinor, while on the other hand Ptirnasaiiix, rich as it is in forms in the Old World, 

 has only a few somewhat scattered, subordinate forms in the New. 



The Pierids are pretty equally rei)resented on both sides of the Atlantic, especially since some 

 have been transplanted during the last centur}'. 



The Danaids show an extremely close parallelism. With only a single species crossing the 40 th 

 degree of N. latitude, their number so increases in the tropics as to become dominant, and the number of 

 very closely related forms would be almost equally the same in the Western Hemisphere as in the Eastern 

 if we reckoned the Neotropids, about to be mentioned. 



But the Satyrids are considera])ly less prominent in the temperate zone of the New World than in 

 that of the Old. In the tropics, where the Satyrids wane and tend to give place to other groups, the 

 contrast becomes less. 



Preeminent among American forms are the Ithomiidae, related to Danais, and which have been 

 designated Neotropids, from their characteristic occuri'ence in the Neotropical region. Even the earliest 

 naturalists who made any adequate observations in South America, such as Bates and Wai-lacj:, were 

 astonished at the enormous number of individuals, as well as the multitude of species which occurred 

 together in snuiU and circumscriljed localities; Bates even wondered how the species, often deceptively 

 similar to one another, managed to find out their right mates for copulation. Haase, on morphological 

 grounds, comj)ares with this group, so rich in species, the genus Hamat^ri/a:^ of the Old World, which is 

 equally poor in forms; from the biological standpoint it is better comiiared with Euploat. 



The Nymphalids, as one of the most universal groups, occupy a prominent jiosition in both 

 hemispheres. It is hard to say on which continent their preponderance over certain other families of 

 Rhopalocera is the most conspicuous. It is the Nymphalids which include most of the forms that are 

 common to both hemispheres. ]'aiiess<( (intiopn, Pijramch atrdiii and afidanta, Poli/ijonia r-a/biini, Aygifiiii/s 

 fric/ar/s, frr/ja, frii/f/a, cluiricJca, etc., connect the American fauna with the eastern and to a certain extent 

 form a bridge. 



The Erycinids of the Old World do not come anywhere near the wealth and variety of forms to 

 which this family attains in America. To little over 100 species of the Eastern Hemisphere there are above 

 1000 in the Western, and at the same time the former are comparatively uniform structurally while the 

 latter show manifold diiTerences. America not only produces a number of original forms in this family, but 



