To one who wanders much in the woods and open fields there are few summer scenes more characteristic of the season, than that of a group of milkweeds in full flower, surrounded by a host of brown butterflies busily sucking the nectar from the curious pink blossoms. There are likely to be several species of these winged creatures, but in many regions of America the largest and most conspicuous will generally be the Great Spangled Fritillary. This butterfly is easily recognized by its large size and its combination of two colors of brown, with whitish or silverish spots scattered over the lower surface of the wings.
The life-history of this insect is of peculiar interest on account of the way in which it passes the winter. The mother butterfly remains upon the wing through many weeks in summer, so that toward the end of August or early September a large proportion of the specimens have a decidedly frayed appearance. They are patiently waiting for the season of the year when they can deposit their eggs, apparently knowing by instinct that this must not be done until early autumn. When the proper season arrives they lay their eggs upon the leaves or stems of wild violets, apparently without much reference to the particular species. Sometimes they have been reported simply to drop the eggs loosely upon the violet plant with no attempt to fasten them in place. Having thus deposited the eggs the mother butterflies soon die.
It would not seem strange if these eggs remained unhatched until the following spring, but the fact is that the eggs hatch very soon into small caterpillars that eat off part of the shells in order to escape and sometimes eat also part of the shell remaining after they have emerged. Various good observers have apparently established the fact that these tiny caterpillars eat nothing else before winter sets in. It seems curious indeed that they should not nibble at the leaves or steins of the violet plants in order to be slightly prepared for the long fast that awaits them before they will find food upon the young buds the following spring. The case is somewhat similar to that of the common tent caterpillar which becomes a fully formed caterpillar within the egg shell before the end of autumn, but remains unhatched until the following spring. In the present case the caterpillar hibernates outside of the egg shell rather than within it.
When at last the warm sunshine of spring starts the violets into new growth the tiny caterpillars begin feeding upon the succulent tissues. They nibble away day after day for a week or more before they become so large that they have to east their skin for the first time. They then feed again and continue this process of feeding and moulting until early in summer. They are likely to hide themselves during daylight and have the reputation of being difficult to rear under artificial conditions.
The full-grown caterpillar wanders along the surface of the ground in search of suitable shelter for the chrysalis period. When it comes to a large stone with sides projecting more or less horizontally or a log lying upon the ground or even a large piece of loose bark it is likely to stop and change to the pupa or chrysalis. In this condition it is dark brown in colour and well covered with thickened tubercles, especially along the back of the abdomen.
About a fortnight later the chrysalis breaks open and the fully developed butterfly comes forth. It rests quietly for a time while its wings expand and the tissues harden and then sallies forth for its long period of flight; for this insect is single-brooded in the Northern states at least and the butterflies that thus mature late in June or early in July are likely to remain alive until early in September. So they have a comparatively long life for a butterfly that does not hibernate as an adult.
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