In the development of our knowledge of both birds and mammals as found upon the American continent the experience in many cases has been essentially this: a bird or a mammal was first described from some well-known region of North America, commonly from specimens carried to Europe by early voyagers. Later other species of the same genus were brought to light by various explorers and given specific names. As each section was thus explored a new form differing markedly from the others was found and named. At a later period, when great collections were brought together so that one observer was able to make a careful survey of specimens from all parts of the continent, it was found that many of these species merged into each other through intergrading forms from regions between the localities of the original species. So it has come about that in the case of a large number of our birds and mammals we have geographical races distinctly recognized instead of separate species.
While the study of butterflies has by no means received the degree of attention which has been given the birds and mammals, it is already evident that a similar condition prevails with reference to many species. As the size of collections has increased and more careful studies have been made of the various forms from different regions it has been found in numerous cases that they intergraded to so great an extent that it is impossible to distinguish many species which were formerly considered entirely distinct. One of the most striking examples of this is found in the case of our common Wood-nymph, which is sometimes called the Blue-eyed Grayling. The form which is one of our most abundant butterflies in southern New England and many of the Eastern states was described as Satyrus alope by the French naturalist Fabricius, who also described another species from the Southern states as Satyrus pegala, and a form found in northern Canada was described by the English entomologist Kirby as Satyrus nephele. Various other forms from isolated regions have been given specific names by other authorities. (See plate, [page 81].)
During recent years many collectors have gathered these butterflies from all parts of North America and many specimens have been grouped together in the more important collections. When this occurred it became easy to see that this is essentially a variable species which under varying climatic conditions has assumed slightly different forms, so that we have a good illustration of well-developed geographical races. The more important of these are indicated in the synopsis of the Meadow-browns on [page 227].
The Similar Life-histories
One good indication that these varying forms all have a common origin is found in the remarkable unity of their life-histories. It is essentially the same in all. The mother butterflies lay eggs late in summer upon the leaves of grasses and perhaps other plants. About three weeks later these eggs hatch into small caterpillars that immediately become lethargic and begin their hibernating condition without eating any vegetation. They remain thus fasting until spring when, after the weather warms up sufficiently, they begin to feed upon grasses and perhaps other herbage. But they have lots of time in which to complete their growth and they are very moderate in their eating and their movements. They grow slowly so that they do not become mature as caterpillars until June. They then change to chrysalids to emerge as butterflies during July and August. The female butterflies remain upon the wing for some weeks before they begin to lay their eggs. We thus have in this case an adaptation to single-broodedness in practically all stages of the insect's life. The twelve months of the year must be passed and egg, larva, chrysalis, and butterfly each seems to try to do its part in prolonging its period of life.
These butterflies are especially common along streams and near the borders of woods, as well as in upland pastures and meadows. They are interesting creatures with characteristic manner of flight. They are by no means so easy to capture as one might think who sees them apparently going with slow, erratic motions from flower to flower. Mr. S. F. Denton, a collector of long experience, has written this interesting paragraph upon this point:
"As the flight of these insects is weak, they have been obliged to resort to a number of tricks to outwit their enemies. In capturing these butterflies the collector will very soon become acquainted with their modes of escape, which are very interesting and show no small amount of cunning, scarcely to be looked for in an innocent little butterfly. Their first plan of escape on being disturbed is to make directly for a clump of bushes into the thickest part of which they dive and there remain until the danger is past. If one is startled from the grass at some distance from a safe retreat and the collector overtakes him, he will immediately dodge backward and forward, at one time high in air and again low down near the grass tops, and in spite of his slow flight keeping well clear of the net. If the net is at last brought very close to him he will try his last desperate scheme to elude his pursuer and shutting his wings quickly together will drop into the grass, disappearing as if by magic. If it were not for the cunning of the frail little creatures they would doubtless have gone to the wall long ago in the struggle for existence."
The Southern Wood-nymph
Cercyonis pegala
This large southern butterfly is sufficiently distinct from the other Wood-nymphs to rank as a separate species. The yellow blotch has expanded into a large band extending practically across the front wings. On its upper surface there is one eye-spot in the male and two in the female. It is abundant in the extreme Southern states and has occasionally been taken much farther north.