to an Insect Fauna of the Amazon Valley. 227 



same genus, when distributed over a wide extent of country, and 

 subjected to different local conditions. For instance, of three 

 allied species of Morpho, one (Helenor, Cram.) is found without 

 any variation at three stations, in 48°, 56°, and 65° long. The 

 second (31. Menelaus, L. Cram.) is constant from 48° to 5Q°, but 

 becomes changed (both sexes) into a well marked and constant 

 variety at Q5° ; and thence further westward, so completely 

 changed that no individual occurs of the typical form of the 

 species. The third (il/. Achilles, Cram.) becomes changed from 

 48° to 56°, and the variety thus produced continues further 

 westward to the exclusion of the type. In another class of 

 species the varieties are not so clearly marked ; sometimes a 

 species is quite constant throughout all its individuals in one 

 locality, whilst excessively variable in another, the typical indi- 

 viduals being in a minority, and in a third completely changed into 

 a well marked and tolerably constant variety. In some species 

 and genera the varieties thus produced would be classed by En- 

 tomologists, without dissent, as mere varieties and without a dis- 

 tinguishing name, and thus, in systematic works, the fact becomes 

 lost to science. In other species, however, the change becomes 

 so great, under the influence however of the same local conditions 

 as the former case, that no difference of opinion would occur as to 

 their being distinct species. In the following catalogue the nature 

 of these different relations between the species will be mentioned 

 under the head of each. 



Gen. Papilio of authors. 



Group. 1. P. Crassiis, and allies. 

 The species of tliis group I place first, on account of their evident affinity 

 with the Ornithoplera of Eastern Asia. 'J'hey have the same stout antennje, with 

 gradually formed, moderately strong, nearly straight club ; similar broad and 

 strong abdominal fold to the hind wings, and pale coloured abdomen in the 

 males. If this relationship be correct, we see how far more highly developed the 

 type has become in the favoured lanJs of the Eastern Archipelago than in the 

 same latitudes of America. The males of the American species have a bold 

 powerful flight, are seldom seen in the shade of the woods, and are attracted by 

 the moisture on the sandy and muddy shores of the rivers, brooks and pools. 

 The females are oftener seen at flowers on the borders of the forest. 



P. Crassus, Cram. 112 C, and authors. 

 $ and 2 . The female does not differ in colours of the wings from the male. 

 The species occurs without any considerable variation from Rio Janeiro to 

 Surinam. It is rare at Par4, but is an abundant species at St. Paulo on the 

 Upper Amazon. 



P. Belus, Cram. 112 A. B. 

 The $ of this species is very well figured by Cramer. Fabricius and Godart 

 confounded it with P. Lyc'das (of which P. Erymanihus is the $) and P. 

 I^iimitor, Boisduval (Sp. Gen. p. 315) professes to describe the 9 1 ^ut I doubt 

 whether he had the true Belus before him when he drew up the description. He 

 gives, as a character of the 5, the row of pale spots accompanying the red 

 lunules of the under surface of the hind wing j but I find that individuals of the 



