Introduction. 



The i>:iant continent of America, which extends fnim the eternal snows of the arctic polar region 

 further south than any otlier continent, is better adapted than any other to the production of an inexhaustible 

 wealth of the most varied animal forms. Ojien almost everywhere to the moisture-laden east winds from 

 the Atlantic, it admits the fertilising rains far into the interior, and thus develops an extensive and finely 

 branched network of watercourses, which, in conjunction with the varying conditions of climate and warmth 

 in the successive zones, call into l^eing a fauna of (juite unique variety. 



Originating from the circumpolar arctic fauna, the entire fauna from southern Canada to Texas 

 acquires a character apjiroaching that of Europe and central Asia. Not only that the dominant animal 

 forms in temjierate North America belong, for the most part, to groups which also play a principal role in 

 the temperate zone of the Old World , the geographical distribution shows also here the most striking 

 analogies. Among the Lepidoptera, Arf/i/miis, Mditaea, l^aiicssa, Ajxitiira, Arctiids and Gatocalas figure 

 ]nominently in both, and as a single outstanding difference, the preponderance of the Hesperids in America, 

 as against the prevalence of Satyrids in the Old World, is manifest even on superficial consideration. But 

 the sum total of the forms to be observed in the northern temperate zone is almost equal in both 

 hemispheres, while one half of the eastern temperate lands — corresponding roughly to the whole of the 

 western — contains about the same numljer of Lejiidoptera as that, namely about 6500 forms. 



This is changed as soon as we reach the tropical zone in America. (Juite suddenly all resemblance 

 to the fauna of the Old World vanishes. The singular and highly characteristic Morpho, Ithomia, Melin.aea 

 and HcUcniiiii^, Castnia and (Tkiiiropii^, Pfricopis; and f'jiUopoila, the wonderful forms of neotropical Erycinids 

 the tailed Hesperids, etc., have no counterparts in the Old World. They give to the South American fauna 

 such a distinct individuality, even compared with that of the cooler parts of North America (north of 

 Mexico), that the lepidopterous fauna of South America may well be designated the most characteristic of 

 the world. What its princij)al pecularities are, has already been pointed out in the introduction to this 

 work, and will be further considered below. 



That in spite of all this we have decided not to separate the North from the South American 

 fauna, as has hitherto been done in zoogeography, under the terms Neotropical and Nearctic, is due to the 

 fact that a basis for any sharp delimitation is wanting here, as it is between the Indian and Australian 

 faunistic regions. Just as the limits there drawn by Wallace are arbitrary, so also in America the 

 otherwise applicable principle of faunistic division fails us. Let us, for exam])le, compare the conditions in 

 America with those of the much more compact continent of Africa: south of the Sahara there is no species 

 of Euchloi-, no Aporia, no Procrh, no true Zijiptoui. no Varif^t^a, no Paranp', no OciiO(/>/iia, in short all the 

 species are absent which in North Africa are the commonest, not to say the most obtrusive representatives 

 of the butterfly world. On the other hand the north has no Ki/phacdru, no Ci/niothoe or Euriiphetic, all the 

 groups of Fapilio and Pierids which are distributed throughout the rest of Africa are wanting, we seek in 

 vain for Amaiiris, which is so characteristic of the whole of tropical Africa, and so on. 



In America there is no such insujterable barrier as is formed by the great Sahara desert of Africa, 

 with its absence of vegetation. Thus we find the otherwise purely South American Neotropids pushing 

 northwards into California, the genus Hrllcoii'nia into Florida, while Ar;///Hni!>, Col/as, Catoada, etc., extend 

 their range southwards on the heights of the Andes; in a word, the two faunas so encroach upon one 

 another that we prefer to draw no boundary at all rather tlian an artificial one; and we do this so 

 much the more willingly because these theoretical considerations iit in with a series of practical ones. 



Among the characteristics of the lepido[)terous fauna of America, which are most ])rominent in 

 South America, we would mention its richness in species. It used to be said that the double continent 

 of America alone contained about as many species as all the rest of the world. This comparison was 

 appUcable so long as we had not learned to tlistinguish all the numerous local forms of certain Jlalayan 



