Results in butterflies:
The chrysalis A, Albany Alope, gave a male not differing from many males taken at Hunter, and which there I always regarded as true Nephele, though off type, being without band, but with a narrow yellow nimbus about the ocelli and connecting them, the edges everywhere fading into the black ground.
On the other hand, the chrysalis B, Hunter Nephele, gave a typical female Alope, with a broad and clear yellow band. The female which emerged in 1877 from the Hunter Nephele before spoken of had both ocelli surrounded and connected by yellow, and stood midway between the types of the two forms.
The two chrysalids from Illinois, as I have said, gave males; one wholly dark, the irides without rings; the other had a faint russet nimbus about them, and over the intervening space was a tint of russet.
The Coalburgh chrysalids produced typical Alope, with broad yellow bands, and like the females which laid the eggs. Therefore outside the belt of dimorphism Alope produced Alope, but inside the belt Alope produced Nephele and Nephele produced Alope.
In conclusion:
In Canada the typical Nephele is the only form representing the genus Satyrus, except that possibly in some localities Alope or intergrades may appear; but if so, it is only occasionally. In New York and part of New England a belt of latitude is passed where in one section or other both these forms fly, besides an endless variety of intergrades. Finally, Alope emerges in the south from this belt as the only form, and inhabits a broad zone, which ends about with the southern line of North Carolina and of Tennessee, but at the southwest flies in parts of Texas, and has become slightly modified when compared with the Alope of the middle States. And to the west, somewhere between New York and Illinois, Alope disappears, and a slightly changed form of Nephele presents itself, and occupies the country to and on the eastern slopes of the Rocky Mountains. In some cases this cannot be distinguished from the typical Nephele, but as a whole, it has taken a departure, and has come to have differences in its larva and chrysalis. I call this form variety Olympus (after the companion of the satyr Marsyas when the latter had his little difficulty with Apollo).
The relationship between Alope and Nephele is in good degree paralleled by L. Arthemis and Proserpina, the first of which occupies the northern half of the Continent, but is dimorphic with the other in a belt of latitude which passes through the northern States from Maine to Wisconsin. Proserpina emerges from this belt on the south, and grades imperceptibly into Ursula, which last changes gradually till it has acquired a type, in Arizona, as different from that in which it manifests itself in Pennsylvania as the Texan Alope is from Alope of New York. This belt is nearly coterminous on both north and south with the belt of dimorphism in the Satyrids. It is worthy of note also that the dimorphism of P. Turnus begins inside this belt.
In this last-named species it has been supposed that the melanic form (confined to the female, Glaucus) first originated by accident, and was afterwards perpetuated and obtained an advantage over the yellow form, and finally in good degree supplanted it throughout its southern area, and that the existence of enemies had much to do with the suppression of one form, while their absence favored the other. What influence has gradually transmuted Alope into Nephele it is difficult to conjecture. It could not here be the presence or absence of enemies which has affected one or other form. And if it is climatic, what can there be in common between the climate of Canada and Illinois which encourages Nephele and extinguishes Alope?
In a second paper I shall speak of Pegala and the Pacific species of this genus.