mingling together. This is not strange, for they have similar habits
throughout their entire lives. So when you see a bevy of butterflies
collected around the midsummer blossoms of the milkweed, you are
pretty sure to find that the Great Spangled Fritillary is associated
with the Silver-spot and probably one or two other related forms. The
Silver-spot is generally decidedly smaller than the one first named
and the surest way to be certain of it is to look on the under side of
the hind wing and see whether there is a broad band of buff between
the two outer rows of silver spots. If this band has disappeared or is
nearly all taken up by the brown ground-color of the wing, you may be
pretty sure we have the Silver-spot Fritillary.
When one has firmly fixed in mind the life cycle of one of these
butterflies, one has a model after which to fashion the rest, for our
several species are remarkably alike in this respect.
The Silver-spots are on the wing for several weeks in summer. During
the latter part of this time the females lay eggs upon violet leaves.
These eggs shortly hatch into caterpillars that go directly into
hibernation, taking no food before winter sets in. The following
spring they feed upon violet leaves and mature in time to change to
chrysalids and emerge as butterflies in early summer. There is but one
brood a year and the species is widely distributed over southern
Canada and the Northern states. It extends south to Virginia and
Pennsylvania and west to Nebraska, Montana, and Washington.
=The Mountain Silver-spot=
_Argynnis atlantis_
If one were able to take a Silver-spot Fritillary and reduce its size
about one third he would have a wonderfully good imitation of the
present species. Except for the size, about the only difference in the
markings is found in the blackish border along the margins of the
Mountain Silver-spot which is not present in the other species. The
buff sub-marginal border line on the under surface of the wings
between the rows of silver spots is also wider in the mountain
species.
The distribution of this butterfly justifies its name. It is
preeminently a northern species, being especially abundant in the
White Mountains of New Hampshire and ranging northward far into Canada
and west through British America as far as the Mackenzie River. A pair
of these butterflies were captured by Merritt Carey on July 16, 1903,
on the summit of Mount Tha-on-tha, in the Nahanni Mountains, at an
altitude of 2,500 feet. The southern limit of its distribution
approximates the isotherm of forty-five degrees. It extends southward
in mountainous regions through New York and Pennsylvania and is found
in Michigan, Illinois, and Iowa. It also occurs in the Rocky Mountain
region of Colorado.
The various species of Argynnis show a remarkable uniformity in their
life-history. Like the others, this butterfly is single-brooded,
laying the eggs on or near violets late in summer, the eggs hatching
into larvae that take no food until the following spring. They then
feed upon the violet leaves, become mature, and change to chrysalids
in time for the butterflies to emerge in June in New Hampshire. These
butterflies remain upon the wing for several weeks. They usually
appear a week or two earlier than Aphrodite or Cybele in regions where
all three species are found. It is worth while for the collector to
take a hint from this fact and do his Silver-spot collecting early.
For after the other species appear it is not so easy to tell which is
Atlantis when the butterflies are on the wing. It is most likely to be
found in open places in the woods, apparently preferring such
situations to the broad expanse of fields and meadows.
=The White Mountain Fritillary=
_Argynnis montinus_
This is distinctly a mountain butterfly, known to be found only near
the top of Mount Washington and other neighboring parts of the White
Mountains. It generally occurs between the altitudes of four thousand
and fifty-five hundred feet. It is doubtless closely related to a
somewhat similar form found farther north and west, but its isolation
from them is complete. Apparently it is single-brooded and very little
is known of the early stages. The butterflies visit the flowers of
goldenrod and those of the alpine sand-wort which are abundant in the
sub-alpine home of this species.
This variety is interesting as a living souvenir of the day when New
England was buried beneath the ice-sheet.
=The Meadow Fritillary=
_Brenthis bellona_
The fact of variation is one of the most universal things in nature.
No two animals are exactly alike and every plant differs from every
other plant. That this is true of the structure of living things is
easily observed but it is not so well known, because not so easily
observed, that most species of animals differ also in the precise
phases of their growth. We know that the variation in form and color
has brought about the remarkable adaptations to surroundings which we
call mimicry and protective coloration. A little consideration will
make it evident that the variation of different individuals in periods
of growth must have led also to the adaptation of the life stages to
the conditions of the changing seasons. This is particularly true in
the great majority of insects which show remarkable adaptations in
their various broods to the seasonal conditions of the localities
where they live.
From this point of view the attractive little Meadow Fritillary is of
especial interest. We are indebted to the studies of S. H. Scudder for
our knowledge of the remarkable variations in its growth. These are so
complicated that in order to make plain the varying conditions it
seems necessary to separate the broods in a somewhat hypothetical
manner.
[Illustration:
THE SILVER-SPOT FRITILLARY
Upper and lower surfaces (_see page 125_)
THE GULF FRITILLARY
Lower Surface (_see page 115_)]
[Illustration:
THE GULF FRITILLARY (_see page 115_)
THE SILVER-BORDERED FRITILLARY
Upper and under surfaces (_see page 131_)
THE BALTIMORE CHECKER-SPOT
Upper and under surfaces (_see page 135_)]
We will begin with what we shall call Group A: The butterflies are on
the wing in May and early June. They have just come from the chrysalis
and continue living for three or four weeks before they deposit eggs,
this time being required in order that the eggs may develop in the
ovaries of the butterflies. These eggs hatch in about a week and the
caterpillars become full grown a month later. They then change to
chrysalids in which condition they remain another week, thus requiring
five or six weeks for the newly laid eggs to mature into butterflies.
Supposing the eggs were laid the first week in June, the butterflies
of this second brood would appear about the middle of July. The eggs
in the ovaries of some of these butterflies also require several weeks
before they are ready to be laid, so that it may be about the tenth of
August when this happens. These hatch and mature to chrysalids during
the next six weeks, the butterflies of this brood emerging about the
middle of September. These in turn lay eggs at once apparently, no
extended period being required for their development before they are
laid. The eggs hatch during the latter part of September and the young
caterpillars feed upon the violet leaves for two or three weeks,
moulting perhaps twice and becoming approximately half grown. They now
stop feeding and go into a lethargic condition in which they
hibernate. Then in spring they awaken and feed again upon the violet
leaves for a short time, becoming mature and changing to chrysalids
sufficiently early to emerge as butterflies late in May.
In this hypothetical group we have a fairly normal condition of a
three-brooded butterfly hibernating in the stage of the half-grown
larva and requiring some weeks for the development of the eggs in the
ovaries of the butterflies in the case of the first two broods but not
of the third.
In another group, which we may designate as B, the conditions may be
similar except that the butterflies lay their eggs very soon after
coming from the chrysalis in the case of all three broods. Obviously
there would be a tendency here for hastening the earliness of the
broods so that the hibernating caterpillars might either become larger
or might go into the hibernating condition earlier than those of
Group A.
In Group C, the variation takes place in the larvae rather than in the
butterflies. These may go on in the normal way up to the time the
caterpillars of the summer brood become half grown. Then they become
lethargic, ceasing to feed and to all appearances going into
hibernation. They remain in this condition until the following spring
when they come forth from their winter's sleep and feed upon the
violets in precisely the same way as the caterpillars of the third
brood of Groups A and B.
In Group D we have another interesting variation of the larvae. These
are the same as C up to the time of becoming lethargic, that is, the
larvae of the summer or second brood become lethargic at the same time
as those of Group C but instead of continuing in this condition until
the following spring they remain in lethargy only three or four weeks,
then they wake up (having apparently then changed their caterpillar
minds) and begin to feed, soon maturing and changing to chrysalids
from which butterflies emerge late in September or early in October.
The result is that these butterflies lay eggs so late that the cold
nights come on apace and the little caterpillars apparently take no
food at all but go into hibernation immediately. In consequence these
must eat for a longer period the following spring, so that the
butterflies into which they mature will be likely not to appear until
well along in June.
It is probable that even this rather elaborate statement does not do
justice to all the variations in the development of this little
butterfly. But perhaps enough has been said to help us to understand
something of the way in which such insects are able to adapt their
life habits to the conditions of their environment. It is easy to see
that if conditions should so change as to give any one of these groups
a decided advantage over the others, the tendency would be for the
other groups to disappear and for the group of favored habits to
survive.
The Meadow Fritillary is common in Canada and the Northern states east
of the Rocky Mountains. It is found especially in lowland meadows and
along the borders of swamps, the very situations chosen by the food
plants of the larva, the blue and the white violets. The butterflies
may be often seen sipping nectar from the various species of mint and
related plants found in such situations. It is commonly associated
with the Silver-bordered Fritillary, from which it is easily
distinguished because it has no silver spots upon its wings.
=The Silver-bordered Fritillary=
_Brenthis myrina_
This attractive little butterfly bears a close general resemblance to
the Meadow Fritillary, from which it differs chiefly by the continuous
row of silver spots along the border of the under side of both pairs
of wings. It is found in the same localities as the other and its
life-history is very similar.
The present species is widely distributed in North America, being
found as far west as the upper Mississippi Valley and the Rocky
Mountains, and southward as far as the Carolinas. In New England and
the Atlantic states it is one of the commonest of the smaller
butterflies.
Beginning with the butterflies which are seen in the fields and
meadows in September, the yearly cycle of this insect may be
summarized in this way: the eggs laid in September hatch in a few days
into tiny caterpillars, some of which become lethargic at once, while
others begin feeding upon the violet leaves and continue thus to feed
until they are about half grown. These then also become lethargic and
find shelter just above the soil surface where they remain until the
following spring. They then begin to feed again upon the violet leaves
and at about the same time the other caterpillars which became dormant
as soon as hatched, also waken and feed upon these leaves. Naturally
those which were half grown at the beginning of spring are likely to
mature and change to chrysalids two or three weeks earlier than those
which were so small at the beginning of the season. Consequently the
fresh butterflies will be found from late in May to the latter part of
June. Presumably those which first appeared have developed from the
larger caterpillars and the later ones from the smaller caterpillars.
The butterflies of this first brood of the season lay their eggs upon
the violet leaves, generally upon the upper surface of the blade, but
occasionally upon the stems or upon near-by grasses. These eggs hatch
in about a week into caterpillars that mature during the next three or
four weeks, coming forth as a second brood of butterflies late in July
or early in August. These in like manner lay their eggs and develop
into a third brood which matures as butterflies in September. These
lay eggs that hatch into the caterpillars which live through the
winter. There are thus three broods of butterflies during the year
and it is probable that there is the same remarkable variation in the
habits of the different broods that have been found in the ease of the
Meadow Fritillary.
_Synopsis of the Fritillaries_
_Gulf Fritillary_ (_Agraulis vanillae_). Expanse 2 3/4 inches. Apex of
each front wing produced into a distinct angle. Upper surface of all
wings reddish brown, marked with black spots and an interrupted black
border, the border on the hind wings enclosing round red-brown spots.
Under surface, so far as it shows when insect is at rest, nearly
covered with large silver-white spots. Found only in the more Southern
states.
_Variegated Fritillary_ (_Euptoieta claudia_). Expanse 2 1/2 inches.
Apex of each front wing produced into a distinct angle. Upper surface
of all wings fulvous brown, thickly marked with buff and brownish
black. A sub-marginal row of black dots on each of the wings, outside
of which is a row of buff crescents on the blackish border. Under
surface, as it shows when the butterfly is at rest, beautifully
marbled in creamy browns and deeper browns. No distinct silver spots
in either surface.
_Diana Fritillary_ (_Argynnis diana_). _Male._ Expanse 3 1/2 inches.
Apex of fore wings rounded. Upper surface of all wings, with a little
more than basal half, solid brownish black and the rest of the surface
orange-brown, marked with darker brown round spots and vein lines.
Under surface light buff, marked with black, with silver crescents and
spots on hind wings. _Female._ Expanse 4 inches. Upper surface of all
wings blackish with bluish or greenish iridescence, and marginal third
marked with blue spots and stripes. These are more prominent on the
hind wings. Under surface slaty brown with prominent silver crescents
on the hind wings.
_Idalia or Regal Fritillary_ (_Argynnis idalia_). _Male._ Expanse 3
inches. Front wings fulvous brown with black spots and markings. Hind
wings black except at base with a row of fulvous brown sub-marginal
spots and an inner row of whitish or bluish white spots. _Female._
Expanse 3 1/2 inches. Similar to male except for larger size and the
fact that the two rows of spots on the hind wings are yellowish brown.
_Great Spangled Fritillary_ (_Argynnis cybele_). Expanse 3 1/4 inches.
General color of wings fulvous brown with black markings on upper
surface and black and silver markings on under surface. The yellow
band between the rows of silver spots on hind wings is broad. There is
a distinct narrow fulvous stripe on the upper side of the hind wing
just inside the outer margin, and a similar stripe along the margin of
the front wing, more or less interrupted by the veins.
_Silver-spot Fritillary_ (_Argynnis aphrodite_). Expanse 3 inches.
Similar to the Great Spangled but a little smaller, and with the buff
yellow band between the rows of silver spots on the lower surface much
narrower and almost disappearing at the rear.
_Mountain Silver-spot_ (_Argynnis atlantis_). Expanse 2 1/4 inches.
Known by its smaller size and the black marginal border stripe on all
the wings, with no brown line dividing this stripe.
_Silver-bordered Fritillary_ (_Brenthis myrina_). Expanse 1 3/4
inches. Known by its small size and a marginal row of silver spots on
the under side of each of the wings, and with many other silver spots
scattered over the under surface of the hind wings.
_Meadow Fritillary_ (_Brenthis bellona_). Expanse 2 inches. Easily
known by the absence of silver spots on all the wings. The wings are
long in proportion to their width.
THE TRIBE OF THE CRESCENT-SPOTS
The members of this tribe have the following combinations of
characters: scaly antennae, with a short stout club some three times
as long as broad, and a pair of slender palpi in which the terminal
joint is only about half as long as the middle one. There may or may
not be a slight ridge running lengthwise of the naked part of the
antennal club.
Although more than fifty distinct species belonging to this tribe have
been found in North America, very few of these are distributed through
the eastern part. Only four are so abundant and widely distributed
that they need be treated of here.
=Baltimore Checker-spot=
_Euphydryas phaeton_
To the naturalist those islands in the seas which are remote from the
mainland have long been of especial interest. The life upon them is
likely to show the results of many generations of living under unique
conditions. The plants and animals are generally distinctive, many of
the species having characteristics which differentiate them markedly
from those upon the mainland. They show in a thousand ways the effect
of isolation and so are of especial value when one attempts to
determine the results of unusual conditions upon living things.
In a somewhat similar way the peat bogs or sphagnum swamps which occur
here and there over a large part of North America are of especial
interest, because in a way they are biological islands in which the
conditions of a long past age are preserved until the present. These
nearly always occur in a little valley surrounded on all sides by
hills. Here the water has collected originally into a pond or lake,
which has been gradually filling up through the growth of peat mosses
and a special set of other plants that develop in such situations. One
can still find many stages in the process. In some bogs the surface
will be practically covered, although the water beneath may still be
so abundant that the matted moss quakes as one walks over it.
Sometimes such bogs are really dangerous because the walker may drop
through to the water beneath. In most of the bogs, however, the little
lake is nearly filled but shows the surface over a small area.
The conditions in these peat bogs have changed little since
civilization began. They are relics of an earlier era which have come
down to us as types of conditions that once existed very generally.
The plant life is unique and consists almost entirely of forms which
are found practically nowhere else. There are comparatively few
animals living in these peat bogs and all of these are likely to be of
especial interest. Among the insects none is more remarkable than the
Baltimore Checker-spot butterfly which has several peculiarities that
differentiate it from the other members of the group. It seems to have
come down to us unchanged from a far remote past and to be living its
tranquil life to-day in precisely the same manner as during the time
when the mammoth and the mastodon were likely to invade its haunts.
The Baltimore is probably the most local in its distribution of any of
the butterflies found throughout Canada and the Northern states. It is
to be looked for only in peat bogs and swamps, and it has a remarkable
unity in its life-history whether it be found in northern Canada or as
far south as West Virginia. The butterfly itself is rather large,
measuring a little more than two inches across its expanded wings and
being colored with an unusual combination of fulvous and yellow upon a
black background. It is present as a rule only from about the first of
June to the middle of July. The eggs, in bunches of from one hundred
to four hundred, are laid upon the leaves of the plant commonly called
snake-head or turtle-head (_Chelone glabra_). They do not hatch for
nearly three weeks; then the little caterpillars emerge together and
usually each eats a little of the empty egg shell. They are then
likely to form a thin web over the under surface of the leaf beneath
which they remain as a small company feeding upon the succulent green
tissue. A little later they are likely to begin the construction of a
miniature nest by spinning a silken web over the young leaves at the
top of the plant. From this time on this silken nest serves as their
home, and they utilize it almost as effectively as do our familiar
American tent caterpillars the nest which they make in the forks of
the wild cherry tree. The Baltimore caterpillars often wander more or
less from their tent-like home but they generally come back to feed as
well as to moult. If the nest is injured by wind or rain, all the
caterpillars turn out to repair it and as the need for new food
supplies arises they also unite to enlarge the tent. This habit of
working together for the common good is very suggestive of the similar
habits of the American tent caterpillars. Doors for going in and out
are left in the tent during its construction.
The tent thus made is likely to be deserted after the first moult and
a new and larger one constructed on another part of the plant. Two or
perhaps three such nests may be made from the time the caterpillar
hatches until after the second moult. The last nest made is very
likely to be upon some neighboring bushy plant or at least to include
some branches of such a plant if the bulk of the nest is made upon
snake-head. For after the third moult the caterpillars stop feeding
and become more or less quiet, thus beginning a nine months' fast,
during which they are simply to wait until the return of spring. This
fast may be begun any time from the middle of August until early in
September, and even when brought indoors the caterpillars cannot be
induced to eat. It is evidently the way in which the species has
bridged over the winter during the thousands of generations of its
existence, and the instinct is so firmly fixed that it cannot be
changed. Even in West Virginia, where the caterpillars would have
plenty of time during the summer to mature as butterflies that would
bring forth another generation of caterpillars that might pass the
winter, the condition is the same as in the far northern regions.
So within the shelter of the silken nest these Baltimore caterpillars
remain from the middle of August until May. Then when the spring
sunshine has sufficiently warmed their cool retreats they come forth
and feed greedily upon the young leaves. They now soon make up for
lost time and complete their growth as caterpillars very quickly.
When full fed they wander about in all directions, each hunting its
own shelter before becoming a chrysalis. Having found a twig or branch
that suits their purpose each hangs downward and changes to a brownish
yellow chrysalis, more or less marked with black. It remains in this
condition for about a fortnight, when it comes forth as the Baltimore
butterfly which thus appears again about the first of June.
These butterflies seem to have some of the characteristics of their
unique surroundings. There are very few flowers in the peat bogs and
it is significant that the butterflies instead of flitting from flower
to flower, as do most of our familiar species, fly rather in a slow
and lazy fashion from leaf to leaf, lighting upon the foliage or
frequently upon the surface of the moss or ground. They seem lethargic
and have little of the animation which we usually associate with the
name butterfly.
In my mind the Baltimore is associated with the White Mountain
butterfly as a survivor of a former geologic period. The latter was
developed under colder conditions and now survives only on a few
isolated mountain peaks; but the former has survived wherever the peat
bog has held its sway during the long ages that the surrounding
landscape has been taking on its present-day condition. Many things in
the life of the Baltimore point to its primitive condition: the laying
of the eggs in loose clusters, the long lethargy of the caterpillars,
the limited flight of the butterflies--all indicate a creature with
habits firmly fixed by long ages of development in a definite
environment.
No collector should feel sure that the Baltimore is not to be one of
his trophies until he has visited in June every peat bog or sphagnum
swamp in his locality. One may search years without finding it, and
then come across a dozen in a single day. I well remember the interest
with which I first found this species on the margin of a great swamp
in Michigan when I was eager for every new butterfly to add to my
collection. I had never seen it alive before and the thrill with which
the first specimen was captured can be realized only by those
remembering similar experiences.
=Harris's Checker-spot=
_Cinclidia harrisii_
This little butterfly so closely resembles the Pearl Crescent and the
Silver Crescent that on the wing it is easily mistaken for them. It
really looks more like them than it does the Baltimore Checker-spot,
which is considerably larger and darker colored than the present
species. This is essentially a northern form occurring only in a
narrow strip of country east of Minnesota and Wisconsin, running on
the north through southern Canada and on the south through Michigan,
New York, and Massachusetts.
This insect is one of the best-known botanists among all the
butterflies. In the very difficult group of asters which has caused
endless confusion to human botanists these insects seem always able to
select the one species--_Aster umbellatus_. It has been repeatedly
found that the caterpillars would starve rather than eat the leaves of
other kinds of asters, and so far as known they have never been found
feeding outdoors upon any other.
These butterflies appear along roadsides and in open fields about the
middle of June. They are often very abundant and are much more
generally distributed than the Baltimore Checker-spot. A few weeks
later the females lay their eggs upon the aster leaves, the eggs being
deposited in clusters of twenty or more on the under side of the leaf.
Early in July the little caterpillars come forth and remain together
in colonies as they feed upon the green tissues of the leaves. Each is
able to spin a silken thread so that wherever they go they weave a web
and they soon protect themselves with a slight silken shelter, which
is suggestive of the nests made by the Baltimore caterpillar. They
continue to live in this manner for several weeks in July and August,
growing rather gradually and becoming approximately half grown before
the frosts of autumn. Unlike the Baltimore caterpillars they now
desert their nests and find shelter at or near the surface of the
ground. Here they hibernate, to come forth the following spring and
feed again upon the new growth of the aster plants, often doing
considerable damage by denuding the young shoots of their leaves. They
become full grown in time to change to chrysalids so that the
butterflies may emerge in June.
=The Silver Crescent=
_Charidryas nycteis_
While this species has not the broad distribution for which the Pearl
Crescent is notable it occurs over a large part of the United States.
Its distribution is bounded broadly by a line running from southern
Canada north of Maine to a point in southern Canada north of Montana,
whence it runs south through Wyoming and Utah to the corner of
Arizona, and thence east through New Mexico and Texas to Ohio and West
Virginia, extending south near the coast to North Carolina. It thus
includes a broad belt of territory occupying fully one half of the
area of the United States.
Throughout this vast area the Silver Crescent is often a purely local
species, occurring abundantly during its brief season in some
favorable locality but seldom being seen in other places near by. In
the north it is single-brooded, the butterflies appearing on the wing
during June and commonly disappearing early in July. Late in June the
females lay their eggs in clusters of a hundred or less on the under
surface of the leaves of various composite plants, notably sunflowers,
asters, and a common species of Actinomeris. A week or more later
these hatch into little caterpillars that feed together in colonies
upon the green tissues of the leaf, taking only the succulent
parenchyma and leaving the network of veins. As one leaf is thus
denuded they migrate to another, in this way passing from leaf to leaf
for several weeks in summer. They continue to feed until about half
grown when they desert the food plant and find shelter at the soil
surface. Here they become lethargic and hibernate until the following
spring. They then arouse again and feed upon the tender leaves of the
new growth, continuing to eat and grow for a few weeks before they
become mature as caterpillars and change to chrysalids. A little later
the chrysalids disclose the butterflies which as already indicated
appear in June.
In more southern regions the life-story of the species is not so
simple. There is at least a partial second brood and it is probable
that in many localities the species is both single-brooded and
double-brooded. In such a case some of the caterpillars go into
hibernation probably about midsummer, remaining quiescent through the
later weeks of summer and all the weeks of fall and winter, while
others would mature to chrysalids and butterflies in summer, and the
butterflies would lay eggs for a second brood of larvae which would
hibernate when partially grown. There are opportunities for careful
observers to do good work upon the life-history of this species in
many parts of its range.
=The Pearl Crescent=
_Phyciodes tharos_
Some years ago Mr. Samuel H. Scudder, the most notable student of New
England butterflies, wrote a delightful essay with the title
"Butterflies as Botanists." From his long experience in rearing the
eggs of these insects he concluded that the egg-laying females know in
a most remarkable way the precise kinds of leaves upon which to
oviposit. He educed many illustrations in proof of the fact and quoted
a remark of Asa Gray, the most eminent of American botanists, that is
worth repeating. At that time Scudder had reason to believe that the
Pearl Crescent laid its eggs exclusively upon the New England aster.
Now the asters as a group have been a source of much trouble to the
botanists who have attempted to classify them as to species and
variety. The various forms are so similar to one another that
different authorities have not agreed as to the limitations of the
species. So when Gray was told that this little butterfly was able
always to distinguish and select for her egg-laying a single species
of this vexing tribe he replied: "If your butterfly selects only that,
it is a better botanist than most of us."
While later observers have found that this beautiful little insect is
not so exclusive in its choice of a food plant as was formerly
believed, it serves to illustrate the fact that a large proportion of
the caterpillars of this group have a very narrow range of food
plants. In nearly every case where the food is thus restricted the
insect feeds only upon species which are closely related to one
another, generally falling within a single genus according to the
classification of the botanists.
There has been much discussion in regard to the way in which the
mother butterfly knows the particular species which she chooses for
oviposition. Experiments apparently have shown that she is not
dependent upon the sense of sight but rather upon the sense of smell,
which as is well known is much more highly developed in insects than
in the higher animals. I suppose it is not very strange that a
creature which has fed from infancy upon leaves with a certain taste
and odor should in its later life respond only to that particular odor
and should neglect all others. In a way the butterfly itself is a
product of the plant and it probably is not necessary to assume that
each butterfly differentiates the odors of all kinds of plants but
only that she responds to the fragrance of the one with which she has
been particularly associated.
[Illustration: _From a drawing by Mary E. Walker_ _See page 153_
THE HOP MERCHANT
Caterpillar, chrysalis, and butterflies. (Reduced)]
[Illustration: Mourning-Cloak
_See pages 112, 171_]
[Illustration: The Viceroy visiting wild carrot flowers
_See page 195_
EXAMPLES OF FOUR-FOOTED BUTTERFLIES SHOWING USE OF THE FOUR LEGS
(Photographed from life)]
This idea may suggest to various observers an interesting point of
view. When you see a butterfly flying leisurely from plant to plant
and alighting upon the leaves rather than the blossom, you may be
pretty sure that she is bent upon egg-laying. Now watch her to see if
she goes at once to the particular kind of leaves she finally selects
or does she stop momentarily upon neighboring plants, apparently
trying to find the one from which the fragrance emanates until at last
she reaches it. Such observations have only rarely been recorded and
if carefully made, notes being taken on the spot, they would have
decided scientific value.
_Abundance and Distribution_
Few butterflies are more abundant or more widely distributed
throughout North America than the beautiful little Pearl Crescent. It
occurs over practically the whole of the United States and Canada and
is found from early in spring until late in autumn. It is a rather
small species with a wing expanse of only about an inch and a quarter,
the upper surface of the wings being that tone of reddish brown called
fulvous, more or less marked with black wavy lines and dots. The under
surface is similar in color, with a small silver crescent near the
outer margin of each hind wing.
These butterflies are not very active creatures, although they are
commonly found in meadows and pastures along brooks and by the borders
of open woods. Instead of laying their eggs singly as do so many of
the more active butterflies, they lay them in clusters, often of a
hundred or more, one layer of eggs being placed above the other upon
the aster leaf. In at least one case observed, the caterpillars hatch
from the layer farthest away from the leaf surface before those of the
layer next the leaf surface emerge. This is an interesting provision,
for were the latter to come out first they would be likely to
disarrange the unhatched eggs. The caterpillars appear about a week
after the eggs are laid and remain together in crowded colonies that
feed upon the upper surface of the aster leaf. At first they eat only
the green tissue, leaving the bare veins, although they are not
careful to denude the entire surface of the leaf as so many other
caterpillars do. As one leaf is exhausted they pass to another near
by, continuing thus to feed in companies for a few weeks. Their
general color is blackish, although the black is relieved with yellow
dots along the back and a band of a similar color on each side. Unlike
the larger social caterpillars of the Mourning Cloak and other
butterflies these larvae do not spin any threads as they crawl from
place to place, so there is absolutely no nest made upon the aster
leaf. This may possibly be correlated with the fact that these
caterpillars are sluggish creatures and when disturbed drop quickly to
the soil beneath.
When the caterpillars are full grown, they fall or crawl to the ground
and scatter more or less in search of shelter. Each attaches itself to
any protection it may have found and changes to a grayish or brownish
chrysalis more or less angular. It remains in this condition for a
period that varies greatly with the weather conditions, averaging
about two weeks.
There are two distinct forms of these butterflies which vary so
greatly that they were once considered separate species. They are now
known, however, to be only seasonal variations. In New England two
broods of the insect occur, one in spring, the other in summer. The
spring form is called technically _Phyciodes tharos tharos_. In this
form the under surface of the hind wings is very distinctly marked
with blackish spots. The summer form is called _Phyciodes tharos
morpheus_. It is noticeably larger than the spring form and it has
very few markings on the under surface of the hind wings.
_The Yearly History_
As it occurs in New England the yearly history of this little
butterfly runs something like this. The spring form of the adult
appears in May and lays eggs upon the aster leaves. These eggs hatch
into caterpillars that feed upon the aster leaves for several weeks
and then change to chrysalids, remaining in the latter stage ten days
or two weeks. They then come from the chrysalids in the form of the
summer butterflies which begin to appear about the middle of July and
continue to emerge for at least a month. These lay eggs upon the aster
leaves again and the little caterpillars that hatch from them feed for
a few weeks or until about the last of September. They are then only
partially grown, but they make no attempt to complete their
transformation at this time. Instead they drop to the ground and go
into hibernation, remaining in this condition until early the
following spring. They then begin feeding again and complete their
development in time to emerge as the spring form of the butterfly in
May.
Some very interesting experiments by William H. Edwards have shown
that the smaller, darker spring form of the butterfly is due to cold.
He placed upon ice chrysalids that would normally produce the summer
form and found that the specimens so treated produced the spring form.
This butterfly is one of the best known examples of the variation in
the yearly cycle due to differences in latitude. This is readily shown
by a brief summary of its life-history, from north to south.
In the far northern climate of Labrador there is but one brood a year
and the butterflies belong to what I have been calling the spring
form. The butterflies appear on the wing in early summer, lay their
eggs upon the aster leaves, and die. The eggs hatch into caterpillars
that feed for several weeks, then become dormant and remain in such
shelters as they can find until the following spring. They then change
to chrysalids to emerge as butterflies a little later. There is thus
but one brood a year and the only form of the butterfly is the small,
darker colored variety.
As far south as southern Canada there is a slight variation in this
yearly cycle. The spring form of the butterflies appears in May and
lays eggs. The eggs hatch into caterpillars; part of these
caterpillars mature within a few weeks, change to chrysalids, and come
out in July or August as the larger summer form of the butterfly,
which in turn lays eggs for the caterpillars that are to winter over
in a dormant condition and mature the following season. But the
significant fact is that not all of the caterpillars which thus have
hatched in spring go through this cycle. Part of them become dormant
when partially grown and continue dormant through summer, autumn, and
winter, just as they did in Labrador. Then in spring they develop into
the spring form of the butterfly, along with the caterpillars that
have hatched from the eggs laid in summer. There is thus what is
called an overlapping of the broods.
Farther south, in southern New England, the life-history is more
definitely two-brooded each year, as already described in an earlier
paragraph. Still farther south, in the region of the Virginias, it is
definitely three-brooded, there being at least two summer broods
during the year. How is it that the instinct to become lethargic lies
dormant in the summer broods of caterpillars and shows itself only in
the autumn brood? Is it perhaps due to a reaction to the colder nights
of the later season? If so, possibly one could get interesting light
upon the subject by experimenting with placing the summer caterpillars
temporarily in an ice chest.
_Synopsis of the Crescent-spots_
_Baltimore Checker-spot_ (_Euphydryas phaeton_ or _Melitaea phaeton_).
Expanse 1 3/4 inches. General color purplish black with the upper
surface marked thus: a marginal row of red-brown spots between the
veins; two rows of creamy yellow spots inside of the row just
mentioned; two or three small red and two or three small white spots
near front border of each front wing. Under surface checkered in
red-brown and creamy yellow on a blackish background.
_Harris's Checker-spot_ (_Cinclidia harrisii_ or _Melitaea harrisii_).
Expanse 1 3/4 inches. This species bears a close general resemblance
to the Silver Crescent. It may be distinguished by the fact that the
middle joint of each palpus is of uniform size from end to end instead
of tapering toward its outer end. The tibial joint of the first pair
of legs of the male butterfly is very thick. The upper wing surface is
so marked with black that the tawny red coloring shows only in the
middle.
_Silver Crescent_ (_Charidryas nycteis_, _Melitaea nycteis_ or
_Phyciodes nycteis_). Expanse 1 3/4 inches. This species may be known
from Harris's Checker-spot by the fact that the middle joint of each
palpus tapers from the middle to the tip and that the tibia of each
front leg in the male is slender rather than stout. On the lower
surface of the wings there is a narrow yellowish marginal line.
_Pearl Crescent_ (_Phyciodes tharos_ or _Melitaea tharos_). Expanse
1 1/2 inches. General color much lighter than either of the preceding.
Terminal joint of each palpus less than a third as long as the middle
joint.
THE TRIBE OF THE ANGLE-WINGS
The special characteristic that distinguishes the members of this
important group from the other Nymphs is the fact that on that portion
of the club of each antenna which has not hairs there are three
longitudinal ridges. The tribe includes a large number of our most
familiar butterflies. Nearly all of them are rather large, with bright
attractive colors. They fly freely along roadsides and in orchards,
fields, and meadows so they are commonly seen by every one.
=The Violet-tip=
_Polygonia interrogationis_
The Violet-tip is one of the largest of the Angle-wings, as well as
one of the most beautiful of all our species. It has a wonderful
violet iridescence which is especially marked on the projecting tip of
the hind wing. On fresh specimens, however, it may be seen practically
all over both surfaces of the wings and in bright sunlight gives them
a sheen of remarkable beauty. The expanded wings measure nearly two
and a half inches, the upper surface being marked with dark brown
upon a ground of orange-brown. The under surface has a bark-like
effect in brownish gray brought about by rather indefinite markings of
varying tone. The most characteristic feature is a distinct silver
semicolon on the middle of the under surface of each hind wing. This
marking closely resembles the Greek interrogation point and so the
species was given the specific name _interrogationis_ by Fabricius
early in the history of science. It has since often been called the
interrogation butterfly as a translation of its Latin name, but in as
much as the marking on the wings is not at all like the English
interrogation point, this has led to considerable confusion and people
have considered it a misnomer. It has also been called the Semicolon
butterfly which is correct enough so far as this most characteristic
feature is concerned; but it leads to confusion in connection with the
Latin name. The recent practice seems the better, which is to call it
the Violet-tip butterfly.
_Life-history_
The life-history of this butterfly is much like that of the related
species. Briefly summarized, this is its story:
The adult butterflies, more or less worn and faded from their long
hibernation, appear in fields and pastures in May. They fly for
several weeks sipping nectar from many kinds of spring flowers. The
females search for the leaves of the elm, hop, nettle, false nettle,
and perhaps other related plants on which they deposit their ribbed
eggs either singly or in small groups, it often happening that one egg
will be laid directly on top of another. About a week later the eggs
hatch into small spinose caterpillars which begin feeding upon the
leaves near by. They continue to feed and grow rather rapidly until
they become full size. Each then fastens a bit of pink silk to the
stem of the plant or some other support, in which it entangles its
hind legs and hangs downward to become a chrysalis which is remarkable
for its numerous protuberances and the beautiful silvery and golden
spots along the middle of the back. Within these chrysalids the change
from larva to butterfly takes place, usually in less than two weeks,
so that this new brood of adults appears on the wing early in July.
Eggs are laid by these for a second brood of caterpillars that feed
upon the host plants in the same way as the others, and mature as
butterflies late in August or early in September. These butterflies
visit the fall flowers and suck the juices of fallen fruits, until the
cold weather of autumn warns them to seek shelter for the winter. They
now find crevices within the bark of trees or places in hollow logs or
stone piles or other similar situations, where they close their wings
together, so that only the bark-like under surface shows, and remain
quiet for long periods. They hibernate in this way, coming forth again
the following season to start the cycle for the new year.
In regions where hops are grown commercially the chrysalids of these
butterflies are often called "hop merchants." There is a quaint fancy
that the price of the crop varies with the lustre of the golden spots
upon the chrysalids. When these stand out conspicuously, according to
this fancy, the hops are to sell high--bringing much gold to the
owners. When these are inconspicuous the hops are to sell at a low
price, with a corresponding diminution in the returns. But this fancy
does not apply at all to the chrysalids when they are nearly ready to
disclose the butterfly, for at this time they lose their metallic
lustre.
=The Hop Merchant or Comma=
_Polygonia comma_
There are two species of butterflies which commonly lay their eggs
upon the hop and which resemble each other so closely in their earlier
stages that they are frequently confused by ordinary observers. One is
the Violet-tip or Semicolon and the other is the one which has long
been called the Comma. The chrysalids of both are marked in silver and
gold and the variation in the golden lustre has led hop growers to
deduce from them the probable price of hops. On this account the
chrysalids are commonly called Hop Merchants and the name has been
transferred to the butterflies themselves. (_See plate, page 144._)
The Comma is easily distinguished by the conspicuous silver mark in
the middle of the under side of each hind wing. This bears a striking
resemblance to a comma, hence the name. The butterflies are somewhat
smaller than the Violet-tips and show to a remarkable degree the
angularity in the borders of the wings. The under side is cleverly
marked in imitation of the bark of trees, which is doubtless of much
benefit to the species in eluding observation during the long months
from October until April, when the butterflies are hibernating in such
concealed shelter as each happens to find. The crevices beneath loose
bark, the openings in fallen logs and hollow trees, the interspaces in
stone piles, as well as the interior of buildings, all serve this
purpose.
Like the other over-wintering butterflies, the specimens that come
forth in spring are commonly faded and more or less frayed from their
long wait since bursting forth from the chrysalis. They may often be
seen sunning themselves on bright days in April and May, resting upon
stones or logs in sheltered spots with their wings fully expanded to
receive the greatest benefit from the rays of sunshine.
[Illustration: Eggs laid in string-like clusters on the under
side of leaf. Magnified. (From Holland)]
When spring has sufficiently advanced for the leaves of the elm and
the hop to be fairly well developed, the mother butterflies lay their
eggs in a curious and characteristic fashion. Under a lens these eggs
look like tiny barrels with vertical ribs. They are deposited in
columns, the egg first extruded being attached to the leaf, generally
the under surface, and those which follow are placed one upon the
other sometimes to the number of six or eight, the group thus making a
miniature column. Now if the egg which was first laid should hatch
before the others, when the little caterpillar came out it would be
very likely to cause the others to fall off and when they hatched they
would find themselves in what would be to them an impenetrable forest
of weeds and grasses from which there would be small chance to escape
to reach the elm or hop leaves. To avoid this calamity we find an
interesting adaptation. The egg at the end of the column hatches
first, although it was necessarily the one laid last. The tiny
caterpillar eats its way out of the shell and crawls over the other
eggs to the leaf. Then the others hatch in succession.
The eggs thus deposited by the hibernating butterflies are likely to
be laid late in May or even early in June. They hatch into
caterpillars less than a week later and these caterpillars feed for
about a month, when they change to the characteristic chrysalids in
which they commonly remain for a week or ten days. They then emerge as
the summer brood of butterflies, most of them in New England appearing
during July. These remain upon the wing for several weeks, the females
laying their eggs upon the elm and hop leaves. These in turn soon
hatch into caterpillars that change to chrysalids in August and emerge
as butterflies late that month or during September. This autumn brood
of butterflies is quite abundant for a time but soon seeks the
seclusion of winter quarters to remain until the following April.
There are thus two distinct broods during the year in the Northern
states while as far south as West Virginia there are likely to be
three broods.
These caterpillars at first simply eat small holes in the green
substance of the leaf, but as they become larger each takes up its
abode on the under surface of a single leaf and makes a sheltered tent
in somewhat the same fashion that the Painted Lady does upon the
nettle leaf. The caterpillar eats out more or less of the base of the
blade on each side of the midrib, thus weakening the edges so that
they can be fastened in a tent-like manner by silken threads. This
serves as a resting place from which it sallies forth to feed,
commonly only toward the tip of the leaf. As a result it often eats
itself out of house and home and has to crawl to another leaf and
construct a new shelter.
While the Comma is generally spoken of as a characteristic northern
species it has a very wide range, being found from New England to
Texas and from the Northwestern states to the Carolinas. It is one of
those species which have two distinct forms of coloring. The winter
form has been given the variety name _harrisii_. The butterflies of
this brood are decidedly lighter in color than those of the summer
brood to which the variety name _dryas_ has been given. The latter was
originally described as a distinct species by W. H. Edwards.
_The Change to the Chrysalis_
The manner in which a larva changes to a chrysalis is second in
interest only to that in which a chrysalis changes to a butterfly.
There are not a great many careful descriptions by competent observers
of this process in print. One of the best of these is that by W. H.
Edwards in his splendid work on "The Butterflies of North America," in
which he describes the transformation of the Comma caterpillar. It is
as follows:
"When about to transform, the caterpillar selects a convenient place
on the under side of a projecting rock, or of a fence rail, or of a
weather board of the house, or the midrib of a hop leaf, and having
spun a little button of pale red silk fixes the hooks of its hind legs
therein and hangs suspended, head downward, in the shape of a fishhook
and remains immovable for the space of twenty-four hours, no change
being perceptible except in the color of the skin, which becomes
partly transparent and loses its dark color owing to its gradual
parting from the chrysalis within. Suddenly, and to a looker-on
without any premonitory symptom, a rent takes place in the skin at the
back of the head, just wide enough to allow the passage of the
chrysalis, the head of which at once emerges. By a rapid contraction
and expansion of the folds of the abdomen the larva draws the skin
upward, successively discovering the parts of the fully formed
chrysalid until at last, and in scarcely more than one minute of time,
the entire skin is gathered about the hind feet. It now bends itself
violently to disengage the end of the chrysalis, which is long,
pointed, and hard, furnished with several little hooks, meanwhile
retaining its hold of the skin by the folds of its abdomen until after
a severe effort, convulsively reaching out and feeling in all
directions for the object of its search, it touches the button of silk
and at once grasps it with its hooks and fixes them in it securely.
Then by a twisting motion it manages to disengage the loose skin which
falls to the ground and the chrysalis rests. The whole process is most
interesting to witness and excites renewed wonder with every
repetition at the ingenuity of the means employed and the delicacy of
the instinct displayed. How to strip off the skin and much more the
legs by which the creature is suspended without losing its hold, and
at the same time to securely fasten the chrysalis, is a problem that
would seem impossible to solve; and yet this little insect
accomplishes it unerringly when to fail would be certain destruction.
And not this species only, but the larvae of all butterflies which
form suspended chrysalids, embracing the whole of the great family of
Nymphalidae, that is, a large proportion of all the existing species
of butterflies, undergo a similar transformation.
"The chrysalis is now green in color, soft and indefensible,
susceptible to the slightest injury, and for a few moments the several
parts of the future butterfly may be seen and readily separated; the
wings folded close and enveloping the thorax, the antennae, and
proboscis stretched at length along the back; but very speedily a
complete casing is formed by the exuding from parts of the body of a
viscous fluid, which binds together the tender parts and covers the
whole with a coating like varnish. This soon hardens and the chrysalis
is ready to take its chance against injury."
=The Gray Comma=
_Polygonia progne_
This butterfly is rather darker colored, especially on its under side,
than the one last discussed. The silver marking takes on a little more
definitely the form of an L than a comma, and the under surface of the
wings is darkened by many blackish threadlike lines running across the
veins. When at rest with wings closed these butterflies are very
easily overlooked.
Except for a difference in the food plants of the caterpillar, the
life-history of the Gray Comma is very similar to that of the other
Comma. The butterflies hibernate, and in spring lay eggs singly on the
leaves of currants, gooseberries, and related plants. The eggs soon
hatch into caterpillars that feed upon these leaves but do not make
any suggestion of a nest. They grow slowly and change into angular
chrysalids which disclose the summer brood of butterflies in July.
These lay eggs for another brood of caterpillars which mature into
butterflies in August and September. These generally go into
hibernation before the middle of October, sometimes choosing simply
the under side of a branch where their dark coloring, so near like
that of the bark, is likely to cause them to be overlooked by their
numerous enemies.
=The Green Comma=
_Polygonia faunus_
The Angle-wings exhibit interesting variations in the geographical
distribution of the species. Some are characteristic members of the
Canadian fauna, others of the Alleghanian fauna. Some of those which
are characteristic of the former are scattered south well into the
latter, but the Green Comma is distinctively a northern species--being
found abundantly in the great regions traversed by the trappers of the
Hudson Bay Company and occurring south as far as northern New England,
being very rare as far south as northern Massachusetts. It is abundant
on the higher slopes of the White Mountains.
As one might expect from the short seasons of the far northern regions
in which this butterfly lives, there is only one brood each year. In
consequence the adult butterflies live a long time. Coming from the
chrysalis generally the first weeks in August, they remain upon the
wing a month or more before they go into hibernation. They come from
their winter quarters in May and commonly continue alive until late in
June. Thus it is evident that many of these butterflies must live at
least ten months as adults, an extraordinary longevity for one of
these frail creatures.
The caterpillars are known to feed upon the foliage of several kinds
of plants. These include alder, currant, gooseberry, willow, and black
birch, the last two named apparently being those most often chosen.
Mr. S. H. Scudder called attention to the fact that these butterflies
are able to make a slight clicking noise as they start into flight.
He described his experience in these words:
"Starting up a pair just at my feet on the Mt. Washington carriage
road one day, I stopped abruptly to see whether they would settle
again. After flying a few yards away to escape the cause of their
disturbance, one turned back and dashed straight at my face, turning
only when within three or four inches of my nose, and then suddenly
whisked off with a distinct click as it did so, snapping its fingers,
as it were, in my very face. There was no sort of doubt about this
click, though if it had not been made so close at hand it would
probably not have been heard. But other butterflies in the tropics
have long been known to emit sounds like this, which can be heard at a
considerable distance; others, including some of our own butterflies,
are known to produce a rustling sound by the rubbing of one wing upon
another; and movements of one sort and another have been so often
observed, as of the opposite rubbing of the erect wings in most
Lycaenids, and the tremulous agitation of the wings in many different
sorts when excited, as to leave little doubt that sounds made by
themselves and for the advantage of warning their brethren play a not
unimportant part in the lives of butterflies."
[Illustration: _See page 233_
MONARCH BUTTERFLY IN RESTING POSITION]
[Illustration: _Photograph by Miss J. Brooks_
_See pages 17, 232_
FLASHLIGHT PHOTOGRAPH OF MONARCH OR MILKWEED BUTTERFLIES
IN MIGRATION]
[Illustration: THREE ANGLE-WINGS: UPPER SURFACE
The American Tortoise-shell (_see page 182_)
The Red Admiral (_see page 160_)
The Violet-tip (_see page 150_)]
[Illustration: THREE-ANGLE WINGS: LOWER SURFACE
The American Tortoise-shell (_see page 182_)
The Red Admiral (_see page 160_)
The Violet-tip (_see page 150_)]
[Illustration: _From a drawing by W. I. Beecroft_
_See page 163_
THE PAINTED BEAUTY
Caterpillar, chrysalis, and butterfly]
=The Red Admiral or Nettle Butterfly=
_Vanessa atalanta_
Among the weedy plants which have been intimately associated with
mankind ever since his slow upward progress in civilization began, the
nettle has probably played almost as important a part as the thistle.
While it lacks the winged seeds of the latter it is even more
effectually protected from the attacks of vertebrate enemies on
account of its irritating hairs. At any rate, nettles of various kind
are widely distributed over the earth's surface, and consequently it
is not surprising that the Nettle Butterfly or Red Admiral should be
almost as cosmopolitan as the Thistle butterfly. The two species are
closely related in structure and habits and the life-history of the
one is very similar to that of the other.
About the middle of May one may see in open fields and along sunny
highways these Red Admirals flitting from flower to flower, or
stopping occasionally upon green leaves in search of opportunities to
lay their eggs. Should you observe them closely you might notice that
some of them seemed frayed and worn while others seemed perfectly
bright and fresh.
_The Life-story_
Late in May and early in June these butterflies deposit their eggs
upon the leaves of the nettles. As a rule only one or a few eggs are
laid on a leaf, but when the butterflies are abundant many leaves upon
the plant may become infested. About a week later the egg hatches into
a larva, which is likely to eat more or less of the empty shell before
crawling up the stem of the plant to the unfolding buds at the top.
Here it makes its first nest by webbing together the still closed
upper surface of a leaf not yet unfolded. It is thus able to furnish
itself with protection from weather and enemies, as well as an
abundant supply of succulent food. It remains in this first home about
a week, then it casts its skin, still within its protection, and stays
until it has recovered after the process. It now migrates to another
larger, expanded leaf where it very cleverly proceeds to construct its
second nest. In order to do this it weakens the midrib at the base of
the leaf by biting nearly through it. Then it cuts a hole in the blade
of the leaf at the base in such a way that the margins are made to
droop, so that they can be fastened together with silk to form a
little tent. We thus have a tent-like nest hanging down from the stem
of the leaf on the under side of which the caterpillar will find
shelter, while near at hand is the green tissue of the inner surface
of the leaf waiting to be eaten. This improvised tent serves as the
home during this second stage of the caterpillar. Here also the second
moult commonly takes place, after which the caterpillar migrates to a
new leaf and constructs its third nest. The rest of the story of the
caterpillar's life consists of similar chapters. After each moult a
new tent is formed and even the chrysalis is often hung within the
last one.
The eggs which were laid late in May develop into butterflies during
July. These in turn lay eggs for the second brood of caterpillars most
of which develop into butterflies late in August or early in
September, but some of which apparently remain in the chrysalis stage
unchanged throughout the winter, and mature as butterflies about the
middle of the following May. This is the explanation of the fact
mentioned at the beginning of this discussion that one can find late
in spring and early in summer some butterflies which seem worn and
frayed while others seem perfectly fresh. They are all the progeny of
the midsummer brood of the previous summer, but some of them have been
living as full-grown butterflies through eight long months of
tempestuous weather, while others have just been disclosed from the
protecting walls of the chrysalis.
The world-wide distribution of this butterfly is shown in the
statement that it occurs throughout Europe, and in North America from
Newfoundland to Cuba and Guatemala. It is a safe guess that it is
found in practically all localities where nettles grow.
It is not alone the association between a butterfly caterpillar and
its host plant which has been brought about during the long ages
through which one generation has been succeeding another, but there
have been also many developments of similar associations between the
caterpillars and their parasitic enemies. The Red Admiral is a good
example of such a development. During its long growth as a species it
has been exposed to attack by vast numbers of tiny foes which live at
the expense of other insects. Several of these foes have found in the
bodies of the caterpillars good opportunities for growth, so that now
the Red Admiral, as a species, has to reckon with many enemies among
these tiny parasites. The interaction between caterpillar host and
uninvited parasitic guest has much to do with the great irregularity
in the numbers of the butterflies. It is simply another example of
that complicated struggle for existence, by means of which nature
keeps ever a fairly even balance of her myriad forces.
=The Painted Beauty=
_Vanessa huntera_
One of the most interesting phases of the study of butterflies is to
learn how often they take advantage in their life-history of any
peculiarity of the food plant which has a protective value. The
Painted Beauty is an excellent illustration of this. The caterpillar
feeds upon the leaves of the common Everlasting or Gnaphalium. This is
an abundant and widely distributed plant, found along roadsides and in
fields and pastures. It is notable for the woolly covering on stems,
leaves, and flowers--this dry, hairy surface being so evident that the
flowers will apparently continue in blossom when they have dried,
hence its common name Everlasting or, as the French call a similar
flower, Immortelle. (_See plate, page 161._)
The utilization of the hairs upon the leaves is begun by the mother
butterfly when she lays her egg upon the upper surface, pushing it
down among the hairs so that it is almost concealed. Should you be
fortunate enough to find one of these eggs you would see that it is a
small, yellowish green object, looking like a tiny barrel with several
vertical ribs upon its surface. A few days after the egg is laid it
hatches into a minute caterpillar that begins eating off the hairs
where they are attached to the leaf, in such a way that it soon has a
free space beneath a bunch of these hairs which it has more or less
matted together by means of silken thread. The little caterpillar has
thus provided for itself a protecting nest that effectually conceals
it from birds or other enemies. It now begins feeding upon the
succulent surface of the rather thick leaf, where it has removed the
hairs. After several days of such feeding it moults, still under the
shelter of its hairy covering. This process of moulting and feeding
continues for two or three weeks, the caterpillar occasionally making
a new covering as needed for its food supply.
The later nests are likely to be made by folding two or three leaves
together, binding them with silken thread. The caterpillar in doing
this takes advantage of the fact that the terminal leaves are vertical
before they have spread out, so that it is a comparatively simple
matter to make a little house by binding their edges together with
silken threads. The larva feeds upon the inner walls of the house it
thus constructs, and as it becomes larger the buds and blossoms are
also utilized for food.
When the caterpillar is full grown it thus finds itself fairly well
concealed within a very substantial sort of a home. Many of them have
the apparent good sense to realize that this is as safe a place as
they are likely to find for shelter during the period of the
chrysalis. So the caterpillar makes the nest especially secure near
the centre of what might be called the ceiling and in this web it
entangles its hind legs and hangs downward, preparatory to changing to
the chrysalis. A few hours later the skin splits apart and is wriggled
off, leaving the chrysalis hanging in place of the caterpillar. About
a fortnight later the butterfly emerges and crawls at once to the
outside of the nest, where it rests quietly while its wings expand and
its tissues harden. Then it flies away in search of the nectar of
thistles and many other flowers which it visits freely.
This Painted Beauty is a wonderful example of harmonious coloring. The
general tone of the upper surface of the wings is fulvous, with some
distinct white markings on a blackish background at the outer angles
of the front pair. There is also more or less blackish shading on the
base and margin of all the wings with an indistinct row of about four
dots, more or less run together, near the margin of the hind wing. The
under surface of the wings is even more beautiful than the upper, and
furnishes a striking example of flower-picturing. There is a little
fulvous background near the middle of the front wings, but the rest of
the surface is spotted and striped with blotches and circles of gray
and brown in a most intricate design. On each front wing near the
outer angle are three indistinct eye-spots in a row, and on the outer
half of each hind wing there are two bull's-eye circles, one smaller
than the other, which form the most conspicuous feature in the marking
of the insect.
When full grown the caterpillars are a little more than an inch long
with a general color of velvety black, marked with fine yellow lines
and more or less covered with bristly spines. There is also a distinct
row of whitish spots along each side beginning a short distance back
of the head.
This is a widely distributed butterfly, occurring from Canada to the
Southern states and beyond. In most northern regions it seems to be
two-brooded, the butterflies commonly hibernating as adults; but
sometimes the winter is passed in the condition of the chrysalis.
Along its southern range there are three and perhaps four broods each
year.
=The Painted Lady or the Cosmopolite=
_Vanessa cardui_
Our story of this beautiful butterfly ought really to begin with that
of one of the most successful plants in the world. Now a plant is
successful from its own point of view when it is able to multiply
abundantly in many different sorts of situations and to spread easily
over a large area. The plant I have in mind is the thistle, which
from time immemorial has been one of the commonest neighbors of man.
It is found over the whole habitable globe, as well as in many parts
which are scarcely habitable. It has many advantages in its struggle
for life. The roots penetrate deeply into the soil; the thickened,
spiny leaves are so protected by their juices and their spines that
they are molested by very few enemies; the flower stalks are also
clothed in a similar armature; and the great heads of flowers are
surrounded with prickly involucres that generally prevent their being
eaten by browsing animals or even by phytophagous insects. The
brightly colored blossoms are abundantly provided with nectar and
pollen, and they attract great numbers of bees, moths, and
butterflies, in order to bring about cross-fertilization. But all of
these advantages are of little significance so far as wide
distribution is concerned, compared with the feathery seeds which are
produced in such abundance and so generally scattered by the slightest
breath of wind that the word thistle-down has come into general use to
express a lightly moving object. These airy seeds have been riding on
the wings of the wind all over the surface of the earth for untold
millions of years. Doubtless during severe storms they may be carried
thousands of miles, and it is easy to think that one of them might
readily go half-way round the world before it found a resting place.
Wherever such a seed alighted and found the condition of a moist soil
and slight protection, it would be likely soon to spring into growth
and to start anew the development of its ancient race.
The thistle, however, has not been entirely unmolested during its
aeons of existence. There has been developing along with it one of
the most beautiful of our butterflies which has received various
scientific names and the common name of the Painted Lady, although it
is also often called the Thistle Butterfly and the Cosmopolite, which
latter title perhaps is to be preferred. This butterfly, however, can
scarcely be considered a troublesome enemy of its host plant, for it
is seldom sufficiently abundant to injure the thistle appreciably. The
relation between the two is rather suggestive of that mutual
toleration by which two living things develop together with advantage
at least to one and without serious disadvantage to the other. The
universal distribution of the food plant has led to a like
distribution of the butterfly. Consequently the Thistle butterfly has
long been recognized as the most cosmopolitan species of its group.
(_See plate, page 176._)
Aside from the wide distribution of its food plant and possibly
correlated with it through the diversity of climatic conditions under
which the insect has developed, this butterfly is remarkable for its
powers of flight. Many instances are known where it has been taken at
sea long distances from land. This is due not only to the propensity
of the individual for taking aerial journeys, but also to the fact
that this is one of the butterflies which has the instinct to
congregate in swarms and to migrate long distances when thus
congregated. In 1879 such a flock started from Africa and migrated to
Europe.
One of the most remarkable things about this butterfly is our
ignorance of what it does with itself in winter. American
entomologists are agreed that the adult butterfly hibernates, but
where it does so seems not to be known. Here is an excellent
opportunity for some young naturalist to go scouting, hunting in board
piles, under loose bark, or with a flashlight searching the interiors
of hollow trees to find between November and April living specimens of
this butterfly. Such a discovery would be a real service to science
and should at once be made known through some scientific journal. In
Europe there seems to be a belief that the insect hibernates partially
at least in the condition of the chrysalis.
_The Life-story_
While we may not know just where the butterflies have been throughout
the winter, we do know that in southern New England they begin to be
seen in fields and along roadsides about the middle of May. Many of
the specimens then have a ragged appearance which is a pretty good
indication that they came from the chrysalis the fall before and have
been lying concealed through all the weeks since. These butterflies
lay their small greenish, barrel-shaped eggs on the leaves of the
thistle. The mother butterfly chooses the location rather carefully
and deposits only one egg upon a leaf. The butterflies continue thus
to visit flowers and to lay eggs until about the middle of June when
apparently they perish.
About a week after the egg has thus been laid, it hatches into a small
spiny caterpillar which does not take the trouble to devour its egg
shell as so many other caterpillars do. Instead it crawls around to
the lower side of the leaf and gnaws off enough of the silken surface
of the leaf to furnish material for making a webby covering, the leaf
particles being woven together by threads from the caterpillar's
mouth. In this way the little creature soon provides itself with a
snug enclosure which serves it as a temporary home. It remains in this
home much of the time when not eating, going out occasionally to feed
upon the green tissues of the adjacent parts of the leaf.
This first home of the young caterpillar, made as it is as a flat
blanket upon a flat surface, can be used only by a very small larva.
Consequently, the caterpillar soon finds these quarters too cramped
and it deserts them to make a new home with larger space. This second
nest is commonly made on the upper surface of a leaf, the edges of
which are likely to be more or less drawn together and other supports
connected from other leaves or a near-by stem. The caterpillar
continues to use this nest number two as a place for remaining when
not feeding and for protection during the process of moulting. But
even this larger nest is likely to be given up about the time the
caterpillar becomes half grown, and a third nest is begun in the upper
part of the plant. This is likely to be very commodious, its walls
being made of leaves or stems bound together by a silken web. Within
this the caterpillar completes its growth, going out and in through
one or more doors when it wishes to feed. Sometimes it even remains
within this nest during the process of changing to the chrysalis,
hanging downward from the upper part in much the same way that the
caterpillar of the Painted Beauty butterfly does. In case it leaves
the nest when fully developed it generally finds a place near-by in
which to pupate.
About ten days after the caterpillar has changed to a chrysalis it
changes again to the adult butterfly. In southern New England these
butterflies appear about the middle of July and lay eggs soon
afterward, these eggs hatching into butterflies that change to
chrysalids and change again to butterflies late in August or early in
September. This autumn brood doubtless furnishes the butterflies that
will be seen upon the wing the following May, so that it is pretty
certain that they must find some shelter in which to pass the
intervening months.
The full-grown caterpillar of the Thistle butterfly is about one and a
quarter inches long and of a general yellowish color, more or less
marked with blackish as well as with paler lines of color. There are
many transverse rows of spines along the segments, each yellowish
spine having a circle of smaller ones at the top.
Notwithstanding its fondness for thistles, these caterpillars
occasionally feed upon various other plants. One might readily expect
them to be able to live upon other composites upon which they are
found, but it seems a bit strange that they should be recorded as
being "especially fond of mallows."
=The Mourning-cloak=
_Vanessa antiopa_
One of the most scholarly students of American insects has happily
called the butterflies "the frail children of the air." It seems a
fitting term for creatures so ethereal that they are readily wafted on
the wings of the slightest breeze and so delicate in structure that
they are likely to be sadly mutilated by the lightest touch of human
hand. Such creatures one would say belong to regions of perpetual
summer and have no place in the blizzard-swept winters of our Northern
states.
Yet if one goes into the snow-clad woods during one of the midwinter
thaws one is likely to see in every open glade several dark-colored
butterflies flitting from tree to tree, or resting with expanded
wings in the sunniest spots. These butterflies obviously have endured
the coldest weather and if they are to survive until another season
must continue to endure still more. This species is commonly called
the Mourning-cloak butterfly--not a particularly happy name for so
beautiful an insect. In England it has the more suggestive title of
Camberwell Beauty, and country boys are said to call it the Yellow
Edge butterfly. Its general life-story has already been told on pages
112-115.
The caterpillars of the Mourning-cloak butterflies are restricted to
comparatively few food plants. In regions where they are not
especially abundant, they are likely to be found upon willow, poplar,
or elm. In general, as many observations indicate, they are as likely
to be found upon any one of these food plants as upon either of the
other two; but in certain localities where they become especially
abundant it seems that they are more likely to occur upon the elm. On
this account they have been called the Spiny Elm caterpillars. There
is considerable evidence to show that they prefer the American elm to
other species of the genus, although in the case of willow and poplar
there seems to be little if any preference as to the species.
Miss Caroline G. Soule has seen the butterflies depositing their eggs
upon the white and canoe birch, and it has been recorded as feeding in
Labrador and Europe upon a species of birch. There is one record of
the caterpillars having been found feeding upon the hackberry, and
also of their having fed greedily upon the leaves of rose bushes, and
still another of their having almost defoliated a pear tree. Linden
and nettle are also included in the European lists of the food plants
of this species. (_See plates, pages 145, 176._)
It is evident, however, that all of these, except the three first
named--willow, poplar, and elm--are to be regarded as exceptional
cases, and that the normal food of the species is the foliage of a
plant belonging to one of these three genera.
It has generally been supposed that this species is double-brooded in
central and southern New England, the butterflies of the first brood
appearing early in July. These are said to deposit eggs which hatch
into caterpillars that mature into butterflies early in September.
These butterflies live through the winter, laying eggs the following
spring.
It is very probable that as far north as southern New Hampshire the
species is commonly single-brooded. During one season when the
caterpillars were unusually abundant, a very careful watch was kept
for the second brood in New Hampshire and Vermont by several competent
observers. Only one colony of caterpillars was found and this was at
Durham in the southern part of New Hampshire near the seacoast.
Consequently, it seems safe to conclude that in northern and central
New England, at least, a single brood is the rule rather than the
exception. This involves the conclusion that the butterflies seen upon
the wing early in autumn are the same ones that developed in July, and
that these same butterflies remain alive through the winter and until,
in the following May, they lay their eggs. Thus there is a period of
ten months of existence in the butterfly state, an extraordinary
length of time for a butterfly to live.
To a large extent the butterflies disappear in August, and the
question arises as to what becomes of them. Our observations lead to
the conclusion that they go into summer quarters similar to those
which they seek out for winter shelter. Apparently they fly about for
a few days after coming from the chrysalis and then retire to cool
woods, where under the side of a log or beneath the loose bark of a
dead tree they settle down and to all appearances go to sleep. The
instinct to remain quiet is very strong in these butterflies. In
taking the accompanying photographs, I found that even shortly after
coming from the chrysalis the butterflies when disturbed would fold
their wings with the antennae between them, and drawing the legs
against the body would lie quietly on their sides for a long time.
These same butterflies would also hang downward from a limb by the
hour in the hibernating position as shown in plate opposite page 32.
In the cooler weather of early autumn, the butterflies come from their
retreats and fly about in the sunshine. They are especially likely to
be seen along the borders of woods or in open glades. At this time
they love the sunshine, and will settle in a sunny place to bask in it.
_Going into Winter Quarters_
When the warm days no longer tempt them abroad, the Mourning-cloaks
seek shelter in many sorts of situations--under loose bark, in hollow
trees, under culverts and bridges, in woodpiles, in crevices of rocks,
or alongside logs lying on the ground. In such retreats they remain
until the sunshine of spring again calls them forth.
Prof. G. H. Parker's observations indicate that these butterflies are
very sensitive to changes of temperature, and he has seen the
interesting action of the butterflies crawling into their hiding
places, finding that this takes place each day after they had been
sunning themselves. Thus he writes:
"These butterflies remain during cool spring nights in places similar
to those in which they hibernate in winter, _viz._, in openings in
stone walls, in old out-houses, in openings under the bark of trees,
etc. They retire to these places with considerable regularity, so that
in the open woods, where dozens of individuals may have been seen
flitting about, all may have disappeared a quarter of an hour later. I
have watched their retreat with some care. On a clear afternoon in
early April I took my stand in a woodland where many Mourning-cloak
butterflies were on the wing. They continued actively flying about
till approximately four o'clock, when I began to notice a diminution
in their numbers. By a quarter past four not a butterfly was to be
seen. During the fifteen minutes from four o'clock on I followed two
to their hiding places. One alighted on the front of a fallen tree and
without expanding its wings crept immediately into a large crack in
the bark. The second settled on a stone fence and crept into a hole
between some loose stones. The period during which this occurred was
marked not so much by a diminution of light as by a rapid fall of
temperature."
That the habit of lethargy in cold and of resting upon the bark of
trees is practically universal with this species is shown by a
statement quoted by H. G. Adams in his book, "Beautiful Butterflies,"
published in England in 1871. The writer quoted says: "In a wood on
the summit of the Drachenfels, when the wind was rather keen, I found
numbers resting on the backs of fallen trees in a state of stupor.
They made no attempts to escape and when thrown into the air their
wings barely opened or flapping feebly eased their fall or enabled
them to seek repose on the stem of a rotten trunk."
_Its Rarity in England_
In many books this species is spoken of by its English name Camberwell
Beauty. It is so called because it was first observed in the
neighborhood of Camberwell in the county of Surrey, England. It seems
that in that country it is a very rare species. This is a bit curious
considering the fact that in America it is so extremely abundant. In
his attractive little book quoted above, Mr. Adams begins the
discussion of this species with this statement: "This is the crowning
glory of the British butterfly collector's cabinet, and a happy man is
he who gets a perfect specimen of an insect which is at once so rare
and so beautiful." And later in the same discussion is this further
statement concerning the scarcity of the species: "In neither the
larva nor the pupa state has the insect been found, we believe, in
this country where its appearance occurs, except just here and there a
single specimen or two, at long and uncertain intervals. About eighty
years ago it was seen in many parts of the kingdom and again in 1819,
but not since then although almost every year one or more specimens
are taken or seen."
A curious fact in regard to the Mourning-cloak, as found in England,
is that the border around the wings seems to be much more generally
white than it is with us. J. O. Westwood in his book on British
butterflies describes the margin as of a white or whitish color and
other writers speak of the same fact. Kirby in his "Butterflies and
Moths" makes this comparative statement: "The border is whitest in
British specimens, and perhaps yellowest in American ones." He speaks
of it also as one of the rarest British species. It is sometimes
called by the common name the White Border and also occasionally the
Grand Surprise, appellations which bear out what has been said above
both in regard to the color of the border and the rarity of the
insect.
[Illustration: THREE MORE ANGLE-WINGS
Upper surfaces at left; under surfaces at right, slightly reduced
The Buckeye (_see page 188_)
The Painted Beauty (_see page 163_)
The Cosmopolitan (_see page 166_)]
[Illustration: _From a drawing by W. I. Beecroft_
_See pages 112, 171_
THE MOURNING-CLOAK
Caterpillar, chrysalis, and butterfly]
The Mourning-cloaks subsist upon a considerable variety of liquid food
which they suck through their long tongues. In spring, when they first
come from their winter quarters, they visit the stumps of recently cut
trees and suck the exuding sap, a habit which they continue whenever
opportunity offers. Mr. W. F. Fiske has noticed that they commonly sip
the sap of maple twigs where the squirrels have gnawed the bark. A
little later they visit the willow catkins to suck the nectar secreted
by these blossoms, and still later they hover about the delicate
blossoms of the mayflower, or trailing arbutus, for a similar purpose.
Probably many other flowers are thus rifled of their sweets, although
this butterfly seems to be a less regular visitor to flowers than are
many of its allies. A little later, when the aphids, or plant-lice,
have become sufficiently abundant so that the so-called "honey dew" is
to be found upon the infested shrubs, these Mourning-cloaks sometimes
sip the liquid sweet from the surface of the leaves. In April and May
they occasionally visit the flowers of moosewood, and later in the
season have been observed upon the blossoms of the common milkweed.
From the time the early apples ripen these butterflies may often be
seen beneath the orchard trees, sipping the liquids of the fallen and
decaying fruit.
_The Parasites of the Eggs_
One fine spring morning I came upon a Mourning-cloak depositing a
cluster of eggs upon a willow twig. She was so busily engaged that I
was able to draw near and watch the operation for some time before she
flew away. As soon as she was gone I was much interested to see a tiny
parasitic fly running eagerly over the newly laid eggs, and this fly
also was so busily interested in her work that I was able to cut the
twig off and sit down to observe at leisure through a lens the actions
of the insect. I dictated to a companion my notes of these
observations and so was able to get rather a complete record of the
process of oviposition.
The tiny fly would stop over one of the butterfly eggs, holding its
body vertical with the hind legs far back and the other legs so
straightened out as to hold the front of the body high up. Then it
would insert its tiny ovipositor through the egg shell and proceed to
deposit an egg of its own inside of the larger egg of the butterfly.
At least it seemed a safe assumption that this was what happened
although of course it was impossible to see the smaller egg at the
time. While thus engaged the antennae of the tiny fly were bent
directly downward to the egg beneath. In about a minute the fly
withdrew its ovipositor and after running around for a few seconds
again settled upon another egg and repeated the operation. Then it
tried again on a third egg, after which I got out my watch and began
timing the process. These are the results in the case of the next
dozen eggs that were laid. It required:
94 sec. to lay egg No. 4. Then fly moved around 26 sec.
120 " " " " " 5. " " " " 27 "
83 " " " " " 6. " " " " 20 "
92 " " " " " 7. " " " " 22 "
75 " " " " " 8. " " " " 40 "
90 " " " " " 9. " " " " 42 "
102 " " " " " 10. " " " " 15 "
120 " " " " " 11. " " " " 21 "
120 " " " " " 12. " " " " 18 "
60 " " " " " 13. " " " " 25 "
120 " " " " " 14. " " " " 25 "
60 " " " " " 15. " " " " 50 "
It thus required an average of about two minutes per egg for the
laying of these fifteen eggs. I then caught the little fly and sent
her to Dr. L. O. Howard, our greatest authority on this group of
insects, to learn the name of the parasite. He identified it as
_Telenomus graptae_, a well-known parasite of the eggs of the
Mourning-cloak and related butterflies.
The most interesting thing about this observation was the fact that
the little fly had apparently begun its operation before the mother
butterfly had finished laying her cluster of eggs. There were
thousands of willow twigs in the immediate vicinity. How did this tiny
creature arrive at this particular place at the particular moment when
from its own point of view it was most needed? Had it been riding
around upon the body of the butterfly waiting for the time when she
should lay the eggs? Or was it attracted to them from somewhere in the
immediate vicinity? That this early arrival probably takes place
generally is indicated by the fact that a similar observation had been
made in the White Mountains by Prof. C. W. Woodworth.
The history of the egg parasite after the laying of the egg seems to
be comparatively simple. It soon hatches into a tiny larva that
develops within the shell at the expense of the contents. It finally
changes to a pupa which in turn changes to the little fly that gnaws a
hole through the egg shell and emerges to the outer world.
_The Parasites of the Caterpillars_
After hatching from the egg, the Mourning-cloak caterpillars are also
subject to the attacks of various parasites. One of these is quite
minute, not a great deal larger than the egg parasite. It is a tiny
four-winged fly which deposits many eggs in a single caterpillar. The
eggs hatch into tiny maggots that grow at the expense of the
caterpillar, finally killing it and changing to four-winged flies
again. As many as 145 of these parasites have been known to emerge
from a single dead caterpillar. These little flies are called Chalcids
by entomologists.
There is still another group of four-winged flies, some of which
attack the Antiopa caterpillars. These are much larger than the
Chalcid flies and are called Ichneumon flies. In the case of these,
only one or two parasites develop in each caterpillar or chrysalis.
In addition to these various four-winged flies, there are certain
two-winged flies, called Tachinid flies, that develop at the expense
of the caterpillars. In New Hampshire, during recent years, these
appear to have been the most abundant parasites of these insects. An
egg is laid on the skin of the caterpillar by a two-winged fly,
similar in general appearance to the figure below. The contents of
this egg shortly develop into a tiny grub that burrows through the egg
shell and the skin of the caterpillar into the inside of the body.
Here it remains, absorbing the body substance of its host and
gradually increasing in size. In a few weeks it becomes fully
developed in this grub state. By this time the caterpillar has become
sluggish from the effects of the parasite. If the branch upon which it
feeds is disturbed, the other caterpillars are likely to crawl away,
but the enfeebled victim remains in its place.
[Illustration: Tachinid Parasite. (Slightly magnified.)]
Shortly after becoming full grown, the Tachinid grub breaks through
the skin of the dying caterpillar and, falling to the ground, changes
to a peculiar pupa; the outer skin of the grub turns brown and becomes
hard, forming a protective covering for the body inside. A week or two
later the insect undergoes another change and emerges as a two-winged
Tachinid fly, like the one that laid the egg some weeks before.
_Other Enemies_
Besides those insects that develop on the inside of the bodies of
these Antiopa caterpillars there are other insect enemies which attack
them from the outside and devour them bodily. The most notable of
these, perhaps, is a large beetle commonly called the Caterpillar
Hunter; it is known to entomologists as _Calosoma scrutator_. This is
a very active insect, with large strong jaws, that runs rapidly about
in search of victims. In some cases it has been observed while
destroying many of the Antiopa larvae.
In the Southern states a common reddish wasp--a species of
Polistes--has also been observed attacking these caterpillars, and
there are probably various other insects that destroy them, although
definite observations showing this have not been recorded.
The Antiopa caterpillars are such spiny creatures that comparatively
few birds attack them. They are devoured, however, by the two species
of cuckoos--the yellow-billed and black-billed--and it is probable
that they are sometimes killed by Baltimore orioles and various other
birds. They are also greedily devoured by toads, but of course they do
not often come within the reach of these useful animals.
Even the adult butterflies of this species have to be on the lookout
for enemies. During the long months of their life many of them
probably succumb to the attacks of birds or other creatures. I have
seen but one such tragedy. While riding along a country highway with a
bird-loving friend one spring day we saw a male Maryland yellow-throat
flit by with a Mourning-cloak in his mouth. The bird lit on a fence,
from which I startled him so that he dropped the butterfly, a worn and
faded, half-dead specimen. The places where the bird held the insect
were indicated by missing pieces of the wings.
=The American Tortoise-shell=
_Aglais milberti_
This beautiful butterfly is one of the most distinctive of all our
species. It is of moderate size, its wings rarely expanding more than
two inches, and it has sufficiently irregular outlines to indicate its
relationship with the Angle-wings. The most striking feature of the
upper surface is the broad band of orange-brown extending clear across
both wings a little inside the border. The remaining surface is a
darker brown marked with two orange-brown spots near the front margin
of each front wing and having scattered iridescent scales which show
plainly under a lens. The suggestion of the coloring of a
tortoise-shell is easily seen in these rich brown tones. The under
surface is a wonderful illustration of protective coloring. With wings
closed and resting against the bark of trees or lying beneath the
trees among fallen leaves, it would require a keen eye to detect the
insect. (_See plates, pages 160-161._)
The American Tortoise-shell is distinctly a northern species. North of
latitude forty-three degrees it seems to occur practically from ocean
to ocean, extending far up toward the arctic region. It is commonly
found in British America as far north as Fort Simpson in latitude
sixty-one degrees. There are specimens in the British Museum collected
by the explorer Ross in arctic America, and there are many in our own
National Museum collected in the Hudson Bay region by various American
explorers. In New England the species is abundant at times in New
Hampshire, Vermont, and Maine. In the vicinity of New York City and
Buffalo, New York, it is rather rare. And south of this latitude it is
found chiefly at the higher elevations in mountainous districts. As a
rule it is likely to vary in numbers from year to year, sometimes
being extremely abundant while more commonly it is rather rare. These
are the same sorts of fluctuations that we find in the case of the
Mourning-cloak, the American tent caterpillar, and various other
insects whose larvae live in colonies. The variation is probably due
to the fact that when the caterpillars become unusually abundant they
become correspondingly conspicuous and so provide a shining mark that
is soon discovered by their insect enemies or by various fungous
diseases.
_The Story of Its Life_
In its manner of laying eggs this butterfly differs from most others.
The great majority of our familiar species lay their eggs one in a
place or possibly two or three near together. Some species deposit
several in a group, while some, like the Mourning-cloak, may lay two
or three dozen in a cluster. Very few, however, deposit hundreds in a
bunch. Two of these are the Baltimore and this American
Tortoise-shell. In the case of the latter the eggs are loosely laid,
hundreds together, upon the leaves of the common stinging nettle.
Probably each female can deposit six or eight hundred eggs. In less
than a week the eggs hatch into minute blackish caterpillars that feed
upon the tender tissues of the leaf upon which they were born and then
migrate together toward the top of the plant. In their habits they are
quite similar to the caterpillars of the Mourning-cloak. As each walks
it spins from its mouth a silken thread and the combined effect of
hundreds of these threads is to make a noticeable silken web over the
leaves. The caterpillars remain in colonies, feeding together from day
to day and gradually denuding the upper branches of the nettle plant,
leaving an unsightly silken web as a memento of their presence. This
webbing is very suggestive of the similar result left behind by a
colony of Mourning-cloak caterpillars upon the twigs of elm or poplar.
When about half grown these caterpillars are likely to scatter more or
less in accidental groups which may make small shelter tents from the
larger leaves. In each little nest there may be four or five or more
of the dark-colored caterpillars. From these shelter tents they sally
forth to feed upon the adjacent leaves and a little later become full
grown as caterpillars. Each now wanders away and finding such shelter
as it is able to, spins a button of silk and becomes a chrysalis. It
remains in this condition but a short time before it emerges again as
the beautiful butterfly.
This species is commonly reputed to have three broods a year,
hibernating both as a butterfly and as a chrysalis. It has been
suggested, however, by Mr. W. F. Fiske, one of our most painstaking
entomologists who has studied the butterflies of New Hampshire for
many years, that it is more probably double-brooded with a period of
aestivation during the later weeks of summer. This seems a very
probable condition and it is to be hoped that some observer will make
such a careful study of this species as to settle the point
definitely.
In the case of many butterflies the distribution of the species
coincides with the distribution of the food plant. This American
Tortoise-shell, however, is perhaps the exception that may prove the
rule, for its southward limit is far north of the southern range of
the stinging nettle. Evidently, it is a species which has developed in
adjustment to the cool climate of northern regions or high altitude,
and it does not easily adapt itself to a warmer territory.
=The White-J Butterfly or Compton Tortoise=
_Eugonia J-album_
During bright days in March and April one is likely to find two kinds
of butterflies on the wing in open glades of the woods. One is the
familiar Mourning-cloak and the other is the Compton Tortoise--the
latter generally much less abundant than the former. Both make the
most of the brief periods of sunshine and quickly disappear when the
sky is overcast.
The Compton Tortoise butterflies which are thus abroad in early spring
have been in hibernation since October. They are helping to carry the
species over from one season to another, and as the days become longer
and warmer they appear on the wing more and more, seeking such liquid
food as the field and forest yields during the days of early spring.
The sap exuding from holes in bark made by woodpeckers, or from the
tappings of the maple trees by man, the nectar of willow catkins, the
moisture of roadside pools--these help to yield a precarious
sustenance to these butterflies after their long winter fast. They
remain upon the wing week after week, while spring slowly progresses
in the northern regions they inhabit. When at last the leaves push out
on their food trees--willow, birch, and elm--the females lay their
eggs and then, having lived to what for a butterfly is a ripe old age,
they die, after nearly ten months of adult existence.
Apparently the eggs are laid in clusters on the twigs, although this
seems to be one of the many facts about butterflies awaiting
observation by some careful student. The caterpillars feed together in
small colonies but make no nest. They become full grown in about a
month. They are then nearly two inches long with spinous, greenish
bodies, striped with lighter lines. Some change to chrysalids about
the middle of June and ten days later change again to butterflies, the
first of which appear early in July while others continue to emerge
for nearly a month.
These butterflies may be seen rather frequently from midsummer on,
visiting various flowers and sipping the juices from decaying fruits
beneath the trees. At times they seem to disappear in August to
reappear in October, a fact which has led some observers to suggest
that there is a second brood. The caterpillars of this brood, however,
have never been observed and a much more probable explanation has been
made by Mr. W. F. Fiske who studied the butterflies of New Hampshire
carefully for many years. He found that in the hot summer weather this
butterfly goes into a seclusion similar to that of its winter
rest--that is, it aestivates in summer and hibernates in winter. "The
possibility that the October J-album did not represent a second
brood," writes Mr. Fiske, "was rendered almost a certainty by repeated
observations which failed to disclose a single specimen approximating
in freshness to average August individuals, and the question of their
whereabouts during the interim was unexpectedly answered one warm
August day by my finding several snugly packed away under the shingles
on an old roof. The theory of the aestivation of the butterflies of
this group will explain a good many points hitherto obscure in the
life histories of the other species."
In October these butterflies seek their winter quarters, finding them
in woods and groves. Apparently they commonly rest upon the bark of
the trunk as well as crawl into such crevices beneath loose bark as
they can find. Here they remain through fall, winter, and spring,
except when called into brief periods of activity by the unwonted
warmth of the winter sunshine. Then in spring they come forth again to
lay the eggs for the caterpillars of the new generation.
The fresh butterflies are creatures of exquisitely modulated coloring.
The name Compton Tortoise has reference to the rich brown tones of the
upper wing surface, suggestive of those of fine tortoise-shell. In
fresh specimens much of the surface, especially in the middle and
along the front border, is overlaid with iridescent purple scales.
Near the front outer angle of each of the four wings there is a
distinct white spot, divided near the middle by a darker line of the
vein running through it. The under surface is one of the best examples
of mimicry of gray bark to be found in any butterfly. The tones vary
considerably in different individuals, but in all the protection must
be well nigh perfect when the insect is at rest with closed wings upon
the bark of a tree. The striking angularity of the wing's border
doubtless helps to conceal it, and the habit of dropping motionless to
the ground when disturbed must also have protective value. Near the
middle of each hind wing there is a small white J which led to the
specific name _J-album_.
This butterfly is essentially a member of the Canadian fauna. It
ranges from far north in Labrador, British America, and Alaska, south
as far as Pennsylvania, but toward its southern limit it occurs only
on the higher elevations of mountains like the Alleghanies.
=The Buckeye=
_Junonia coenia_
Some genera of butterflies seem to belong almost exclusively to the
north temperate regions, seldom occurring even in our Southern states.
Others belong equally exclusively to tropical regions, seldom
straying into the north. The Buckeye is an illustration of the latter
group. The genus Junonia to which it belongs is essentially tropical,
as it contains several species which are found throughout the tropics
in both the Old and the New Worlds. In fact, this is apparently the
only species which occurs north of the tropics. It has an
extraordinary range, being found from Cuba to Massachusetts and from
the Atlantic to the Pacific coasts. Toward the northern limits of its
range it is very rare and one of the greatest prizes which the
collector can obtain. In our Southern states it is an abundant and
generally distributed butterfly and, as it hibernates as an adult and
one group follows another throughout the season rather rapidly, it is
likely to be taken at almost any time. (_See plate, page 176._)
The mother butterflies select as food plants for the larvae various
members of either the plantain or figwort families. They lay eggs, one
in a place, upon the leaves of plantain, figwort, gerardia, and
related plants generally near the tip of the leaves. Less than a week
later these hatch into spiny caterpillars which feed upon the green
substance of the leaves during the next few weeks. For the most part
they eat between the veins leaving a ragged effect which may help in
finding them. When full grown they change to chrysalids which hang
straight downward and bear a general resemblance to those of the
Thistle butterfly. Curiously enough, those chrysalids which are
attacked by parasites take on a characteristic golden hue; although
the normal healthy chrysalids are dark brown with a few touches of a
decidedly lighter brown.
In its tropical home, where there is no winter period to interrupt its
growth, this butterfly doubtless continues to develop generation
after generation without any break in the sequence. As the species
goes north, however, there is necessarily such an interruption--in
which case the winter seems commonly to be passed by the adult
butterfly. In our Southern states there are commonly three or four
broods each year, while in the northern parts of its range there is
but one brood a year. In the South there is such an overlapping that
all stages of the insect may be found at one time.
_Synopsis of the Angle-wings_
_I. The Polygonias_
The most angular of the Angle-wings are grouped in the genus
Polygonia. They are characterized by having the outer margin of the
front wings projecting in two places in a way to give an angular
effect, and by having the hind or inner margin distinctly excised
toward the outer end, so that this margin is curved rather than
straight.
_Violet-tip_ (_Polygonia interrogationis_ or _Grapta
interrogationis_). Expanse 2 1/2 inches. Under surface of each hind
wing marked by a silvery semicolon, made up of a dot and a crescent.
_Hop Merchant_ (_Polygonia comma_ or _Grapta comma_). Expanse 2
inches. A white comma with expanded tips on lower surface of each hind
wing. Lower surface of all the wings mottled with brown.
_Green Comma_ (_Polygonia faunus_ or _Grapta faunus_). Expanse 2
inches. A white comma with expanded tips on lower surface of each hind
wing. The lower surface of all the wings more or less mottled with
green toward the margins.
_Gray Comma_ (_Polygonia progne_ or _Grapta progne_). Expanse 2
inches. A white comma with tips narrowed rather than expanded on lower
surface of each hind wing.
_II. The Vanessids_
Our beautiful species of the genus Vanessa may be known by the long
scales that make up the fringe on the wing margins, in alternate
groups of black and white. There are also several white spots on the
upper surface of the outer angle of each front wing.
_Red Admiral_ (_Vanessa atalanta_, _Pyrameis atalanta_ or _Cynthia
atalanta_). Expanse 2 inches. Upper surface of front wings blackish,
marked with white spots on outer angle and a broad orange stripe
across the middle.
_Painted Beauty_ (_Vanessa huntera_, _Pyrameis huntera_ or _Cynthia
huntera_). Expanse 2 1/2 inches. Upper surface orange-brown with
black, white, and blue markings. Lower surface of each hind wing with
two large eye-spots, each extending across two veins.
_Painted Lady_ or _Cosmopolite_ (_Vanessa cardui_, _Pyrameis cardui_
or _Cynthia cardui_). Expanse 2 1/2 inches. Easily distinguished from
the Painted Beauty by the four or more small eye-spots on the lower
surface of each hind wing, each eye-spot being included between two
veins.
_III. Other Angle-wings_
The other common Angle-wings are readily distinguished by the
following characters:
_Mourning-cloak_ (_Euvanessa antiopa_ or _Vanessa antiopa_). Expanse
3 1/2 inches. Easily known by the nearly black wings with creamy white
borders.
_American Tortoise-shell_ (_Aglais milberti_ or _Vanessa milberti_).
Expanse 1 1/2 inches. One of the smallest of the Angle-wings. Easily
known by its small size and the broad orange band extending across the
upper surface of all the wings just beyond the middle. Under surface
dark mottled gray without distinct white markings.
_Compton Tortoise_ (_Eugonia j-album_, _Vanessa j-album_ or _Grapta
j-album_). Expanse 3 inches. Best known by the straight line of the
inner margin of the front wings and the white j on the under side of
each hind wing.
_The Buckeye_ (_Junonia coenia_ or _Vanessa coenia_). Expanse 1 3/4
inches. Distinguished by the large eye-spots on the upper surface of
the wings, one on each front and two on each hind wing. Eyes not
hairy.
THE TRIBE OF THE SOVEREIGNS
No other small group of American butterflies has attracted so much
attention as the species of the genus Basilarchia, which have been
happily called the tribe of Sovereigns. These are rather large
butterflies with rounded wings which are found in one species or
another over practically the whole of North America. Some of them are
of exceeding beauty and all of them present life-histories of
extraordinary interest. At least two of the species are the most
notable examples of the mimicry of other butterflies that are shown in
our fauna. They also present some extremely interesting problems for
the study of natural hybrids and they illustrate in their development
some of the most wonderful cases of adaptation to environment that
have ever been found.
[Illustration: _From a drawing by W. I. Beecroft_
_See pages 268-282_
SOME COMMON SKIPPERS
The Long Dash, male, at top; the Vitellius Skipper, female,
next below; the Canadian Skipper resting on iris flower in the
middle; the Least Skipper, next below; Leonard's Skipper at
rest on leaf, next; and the Sachem Skipper, male, at bottom]
[Illustration: _From a drawing by W. I. Beecroft_
_See pages 195-202_
THE STAGES OF THE VICEROY
The butterfly freshly emerged; caterpillar hung up for
pupation; the chrysalis; the caterpillar feeding]
These butterflies may be considered from so many interesting points of
view that it is a bit difficult to know which phases to emphasize. In
general, there is a striking similarity in their structure and habits
in the earlier stages. The eggs are very nearly alike; the
caterpillars resemble one another so closely that even expert
entomologists sometimes have to decide what species a collected
caterpillar belongs to by seeing what plant it is feeding upon, and
the chrysalids are also very similar.
Some of the more interesting phases in the development of these
insects are discussed in connection with the life-stories of the
different species. A phase which is characteristic to all of them may
well be emphasized here. From the time the caterpillars hatch until
they change to chrysalids they illustrate to a marked degree an
adaptation through structure and habit which must very largely protect
them from attack by birds and other enemies. Their structure and
markings are almost grotesque. The body is covered with strange
club-like appendages and it is colored with a curious mottling of
tones of green, drab, brown, and white which is very difficult to
describe but which suggests, as the caterpillar rests upon rough bark,
simply a bit of bird dung or some natural excrescence. The
caterpillars have the habit of feeding at night and remaining upon
their perches by day, often assuming positions which are very unusual
among insect larvae. Such positions, in which they remain motionless
for hours at a time, are undoubtedly of protective value and help to
conceal the insect. After the caterpillars are half grown they rest
not upon the leaves upon which they feed, but rather upon the bark of
twigs or branches where their peculiar structure is likely to make
them inconspicuous.
The chrysalids of the Sovereigns are also curiously mottled in color
tones that will probably lead to their being overlooked.
Three distinct species of Sovereigns are found in eastern North
America, namely:
The Viceroy, _Basilarchia archippus_.
The Banded Purple, _Basilarchia arthemis_.
The Red-spotted Purple, _Basilarchia astyanax_.
The first species, the Viceroy, has a much wider distribution than
either of the others. It apparently is found in nearly all localities
in which either of these occur, and so includes within its range
almost the whole of the United States and much of Canada.
The second of these, the Banded Purple, is a northern form. It is
found commonly at least as far north as the Mackenzie River region in
British America and southward to central Massachusetts. It also occurs
as far west as Nebraska so that it has a very wide distribution in
northern regions. It is especially abundant in Canada and the White
Mountains.
The third, the Red-spotted Purple, is the characteristic form south of
latitude 42 degrees. Its range overlaps that of the Banded Purple for
about one degree but it is seldom found north of latitude 42 degrees.
It seems to range about as far west as the Banded Purple.