Page:The naturalist on the River Amazons 1863 v1.djvu/330

 sand-bank, from having here observed, for the first time, in ascending the river, one of the handsomest of the many handsome butterflies which are found exclusively in the interior parts of the South American continent, namely the Papilio Columbus. It is of a cream-white colour bordered with black, and has a patch of crimson near the commencement of its long slender tails. In the forest, amongst a host of other beautiful and curious insects, I found another species of the same genus, which was new to me, namely, the Papilio Lysander, remarkable for the contrasted colours of its livery—crimson and blue-green spots on a black ground. This conspicuous insect may be cited as affording another illustration of the way in which species so very commonly become modified according to the different localities they inhabit. P. Lysander is found throughout the interior of the Amazons country, from Villa Nova to Peru, and also in Dutch and British Guiana. In the Delta region of the Amazons it is replaced by a form which has been treated as a distinct species, namely, the P. Parsodes of Gray. In French Guiana, however, numerous varieties intermediate between the two are found, so that we are compelled to consider them as local modifications of one and the same species. The difference between the two local forms is of a slight nature, and many naturalists on this account alone would consider them to belong to the same species; but the numerous existing intermediate shades of variation show how many grades are possible between even two local varieties of a species. In fact, the steps of modification are found