Butterflies Worth Knowing Part 20

THE MEADOW-BROWNS OR SATYRS

FAMILY _Agapetidae_

The Meadow-browns form one of the most distinctive family groups among all the b.u.t.terfly tribes. They are characterized, at least so far as our eastern species are concerned, by their slender bodies and rather large wings, toned in various shades of brown, and marked chiefly with conspicuous and characteristic eye-spots. The larger veins of the front wings are swollen at the base. The caterpillars are rather slender and have a curious division of the last body segment into two parts, which gives them an appearance suggestive of the caterpillar of the Emperor b.u.t.terflies, although the Meadow-brown caterpillars do not have, upon the head, the curious antlers borne by the Emperor larvae.

=The Common Wood-nymph or Grayling= _Cercyonis alope_

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 b.u.t.terflies 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 b.u.t.terflies 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 b.u.t.terflies 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 a.s.sumed slightly different forms, so that we have a good ill.u.s.tration 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 b.u.t.terflies lay eggs late in summer upon the leaves of gra.s.ses 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 gra.s.ses 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 b.u.t.terflies during July and August. The female b.u.t.terflies 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 pa.s.sed and egg, larva, chrysalis, and b.u.t.terfly each seems to try to do its part in prolonging its period of life.

These b.u.t.terflies 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 b.u.t.terflies 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 b.u.t.terfly. 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 gra.s.s 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 gra.s.s 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 gra.s.s, 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 b.u.t.terfly 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.

=The Pearly Eye= _Enodia portlandia_

Most b.u.t.terflies are creatures of open country, basking freely in the suns.h.i.+ne and visiting flowers of many sorts for their nectar food.

Some of them are found at times along the borders of woods and others seek the woods especially in autumn for the purpose of hibernation.

This exquisite Pearly Eye, however, is distinctly a woodland species, being found only in little glades in the midst of woods and apparently seldom even seeking flowers for their nectar. It is commonly considered one of the rarest of American b.u.t.terflies, but many collectors who have searched their regions carefully have been able to find small areas in which the b.u.t.terfly is quite abundant. In such situations it may be looked for in all parts of the United States east of the western limits of the Mississippi Valley and south of Canada, except perhaps the lower part of Florida.

In northern regions this b.u.t.terfly is single-brooded: the adults appear shortly before midsummer and continue on the wing through July and at least part of August. The eggs are laid some weeks after the b.u.t.terflies emerge. The caterpillars feed upon gra.s.ses and apparently hibernate after they become well grown, changing to chrysalids the following spring in time to emerge as b.u.t.terflies in early summer.

These Pearly Eyes have certain characteristics which are of especial interest. No other species presents such exquisite modulation of brown coloring arranged in beautiful circles upon both surfaces of the wings. The males possess, perhaps to a greater degree than any other of our native b.u.t.terflies, the ability to give off a peculiar, pleasant aroma which is noticeable whenever the insects are collected and which at least one careful observer has been able to detect in the open air as the b.u.t.terfly flew near.

For many years Mr. W. F. Fiske made a special study of the b.u.t.terflies prevailing in the region of Webster, New Hamps.h.i.+re. His word picture of the haunts of the Pearly Eye is more adequate than any other which has been published and seems well worth quoting in this connection:

"I have found them in several localities, always in some numbers, but nowhere more abundant than in a little wooded glen in Webster. Here a scattering group of tall pines, a few thick hemlocks, and a young growth of miscellaneous deciduous trees fill up the s.p.a.ce between two rather steep banks. A small trout brook follows close by one of these banks, and near the lower end of the glen, in a s.p.a.ce kept clear of underbrush by the overshadowing influence of the pines and hemlocks, is a little spring, the overflow from which keeps the ground moist for some s.p.a.ce on each side of the channel which it follows to the brook.

This is the great meeting place of these b.u.t.terflies; here they may be seen at almost any time in the day except in the early morning--when they seek the outskirts of the woods--until the shades of evening render their flitting forms indistinguishable. Half-way up the bank on one side, half shrouded in the dense growth of underbrush which is springing up around it, is an old apple tree upon which the sapsuckers work yearly. The wounded limbs, dripping with sap, are frequented by many forms of insect life, most noticeable among them this b.u.t.terfly, and such refreshment added to the moisture which they suck from the margin of the spring is all that I have ever seen them partake."

=The Eyed Brown= _Satyrodes canthus_

For delicacy of gray-brown color tones few b.u.t.terflies can compare with this exquisite creature. It seems indeed to have succeeded in a modest attempt to obliterate itself, for even when the spread wings are placed against a clear white background they can scarcely be called conspicuous and it is very probable that when the b.u.t.terfly is at rest in its native haunts, with wings closed together so that only the very delicate light brown color-tones of the under surface are revealed, it actually becomes invisible.

The upper surface of the wings is broadly washed with a gray-brown color which runs into a suggestion of a lighter band near the outer margin of the front pair. The upper surface of the hind wings is almost uniformly washed with this same brown color which is interrupted only by very fine, double lines at the outer margin and a sub-marginal row of delicate _ocelli_ which are larger than the somewhat similar sub-marginal row of eye-spots on the front wings. The under surface is much lighter in color, with distinct striations extending across the main surface of both wings from front to back and with some very attractive _ocelli_ arranged as a sub-marginal series each with a central white eye.

This is distinctly a northern species, having rather a limited range in Canada and New England. It extends south to Pennsylvania and Ohio and westward to Wisconsin and Iowa. It is more abundant in northern than in southern New England but it is often overlooked by collectors who are not familiar with its haunts. It is especially likely to be found among the tall gra.s.s of swamps and brooks running through lowlands. One of the best ways to discover it is to beat the gra.s.ses in such situations.

The life-history of the Eyed Brown is fairly well known. The eggs are laid chiefly on gra.s.ses and probably at times upon the gra.s.s-like sedges. The larvae feed upon these plants and become nearly full grown before winter sets in. They then hibernate in this larval stage and the following spring complete their growth and change to chrysalids in time for the b.u.t.terflies to emerge in June. There is but one brood a year.

=The White Mountain b.u.t.terfly= _Oeneis norna semidea_

To appreciate the extraordinary distribution of this notable species one must let his fancy carry him back a million years or so until he reaches that old time when the whole northern part of the American continent was covered with an icy coating. Then he must follow the gradual retreating of the ice northward, carrying with it wonderful changes in climate and along with these climatic changes taking northward many plants and animals which were adapted to the cool temperature along the borders of the glacier. As the ice cap retreated most of these arctic forms retreated with it, and all along the lower levels they were replaced by others migrating from the south so that gradually there came about the distribution of plants and animals as we find them to-day.

When, however, the glaciers left the higher elevations of the White Mountains and the Rocky Mountains there were at the summits small areas in which the climatic conditions were of very much the same arctic character as prevailed along the margin of the ice cap.

Consequently conditions were here favorable for the continuation of many of the arctic species which had disappeared from the warmer, lower levels. It was as if we had a great sea of air of a certain warmth and rising above this the islands of the mountain tops, these islands retaining the same arctic features as otherwise are found much farther northward.

Among the animals thus left stranded by the retreating ice cap this White Mountain b.u.t.terfly has perhaps attracted the most attention from scientists. It is a b.u.t.terfly of moderate size which shows in every phase of its structure and its life-history the results of the long process of adaptation to its unique environment. It has been carefully studied by many observers and has been considered one of the most desirable trophies by every collector of insects. As a result, notwithstanding its isolation and the difficulty of studying it, its life-history is better known than that of many a common and widely distributed species.

To appreciate the facts in regard to the structure and life of this b.u.t.terfly one must know that its habitat is confined to a thousand feet or so at the summits of the mountain, that in this area there are no trees or even shrubs worth mentioning, and that the surface of the mountain is covered with rocks between which grow a few stunted sedges and over which grows the ever-present reindeer moss. It is a bleak, bare, gray environment, constantly swept by terrific winds, where snow is seen in August and is likely to remain until June. So the summer season is of briefest duration and the climatic conditions are so severe that one can only wonder how a fragile creature like a b.u.t.terfly is able to survive the twelve long months.

_Habits and Life-history_

From a first glance at the mottled gray-brown wings of these insects one would guess that here was a distinctive example of obliterative coloring, and it is true as all observers testify that when the b.u.t.terfly lights upon the stones and turns sideways, as apparently it does habitually in deference to the force of the wind, it becomes very difficult to see, for the wings are closed and only the rounded, mottled under surface shows. It appears also to have the habit of some of the Graylings when hard pushed of simply closing its wings and dropping to the ground feigning death. In deference also to the winds its flight is just above the surface. Doubtless if it rose high in the air it would be swept away to lower regions where evidently it is unable to survive for long periods.

[Ill.u.s.tration: _From a drawing by Mary E. Walker_ _See page 229_

THE ZEBRA b.u.t.tERFLY On orange leaves and blossoms. (Reduced)]

[Ill.u.s.tration: On a milkweed pod]

[Ill.u.s.tration: _From "Seeing Nature First"_ _See pages 47, 235_

On clematis seed-fruits PHOTOGRAPHS OF A PET MONARCH b.u.t.tERFLY]

These b.u.t.terflies appear early in July and continue on the wing for several weeks. They lay their small eggs upon or near a species of sedge which is abundant on these alpine summits. About two weeks later the eggs hatch into sluggish little caterpillars which feed upon the sedge leaves, apparently eating only at night and hiding in crevices between stones by day. As one would expect from the prevailing low temperatures these caterpillars grow very slowly and apparently a large proportion of them require two years to complete their development. There seems to be some uncertainty in regard to this phase of the insect's life-history, but most entomologists are of the opinion that some of the b.u.t.terflies mature in one year while others require two years: that is, the broods are both annual and biennial.

There is no doubt that the insect hibernates as a caterpillar, and if this statement about the number of broods is correct some of the caterpillars hibernate when very small, and recently hatched from the egg, while others hibernate when nearly full grown.

The full-grown caterpillars change to chrysalids beneath the shelter of the small stones in practically the same sorts of situation which they have chosen for hiding at night or for hibernation through the winter. Here without any b.u.t.ton of silk or silken loop and with scarcely a suggestion of a silken coc.o.o.n they change to chrysalids, generally about the first of June. They remain in this condition for perhaps three or four weeks when they come forth as b.u.t.terflies.

=The Arctic Satyr= _Oeneis norna jutta_

This is another b.u.t.terfly of decided interest because of its geographical distribution. It is normally an inhabitant of the Far North, extending around the North Pole over parts of three continents.

Apparently, the only place in the United States where it occurs is a bog a little north of Bangor, Maine. This locality is called the Orono-Stillwater bog and is the only place where collectors have been able to find this species.