TRANSCRIBER’S NOTE
Italic text is denoted by _underscores_.
Bold text is denoted by =equal signs=.
Some minor changes to the text are noted at the end of the book.
THE BUTTERFLY GUIDE
THE BUTTERFLY GUIDE
A POCKET MANUAL FOR THE READY IDENTIFICATION OF THE
COMMONER SPECIES FOUND IN THE UNITED STATES AND CANADA
BY
W. J. HOLLAND, LL.D.
Director of the Carnegie Museum
Author of “The Butterfly Book,” “The Moth Book,” etc.
_With 295 Colored Figures_
_Representing 255 Species and Varieties_
Garden City New York
DOUBLEDAY, PAGE & COMPANY
1915
_Copyright, 1915, by_
DOUBLEDAY, PAGE & COMPANY
_All rights reserved, including that of
translation into foreign languages,
including the Scandinavian_
To the
BOY SCOUTS OF AMERICA
I dedicate
this Book
_The Author_
PREFACE
Recent advances in the arts make it possible to illustrate books at
much less cost than formerly. An important invention is the process
of printing in three colors from half-tone plates. The author of this
manual was one of the first to use this process in illustrating a work
upon the lepidoptera. When “The Butterfly Book” appeared he received
letters from many scientific friends expressing their wonder. Among
those who wrote to him was Dr. Samuel Hubbard Scudder, the Nestor among
American lepidopterists, who has since passed away. He said: “I am
simply astonished at the fidelity to nature displayed by the plates in
your book, and at the low price at which the new process permits it to
be sold.”
That “The Butterfly Book” met a real need is shown by the fact that
more than thirty thousand copies have already found purchasers. It is,
however, a biggish book. The publishers, Messrs. Doubleday, Page & Co.,
have asked me to get up a little pocket manual of the butterflies,
similar in form to the “Flower Guide,” which has been most cordially
received by the public. I have therefore prepared the following pages,
to which in the gracious phrase of our forefathers I now “invite the
attention of the gentle reader.”
There are more than six hundred species of butterflies found in North
America, north of the Gulf of Mexico and the Rio Grande. Most of these
are figured in “The Butterfly Book.” In this manual two hundred and
fifty-five species and varieties are depicted in their natural colors.
They are mainly the commoner forms, which occur in the more densely
inhabited parts of the United States and Canada. I have, however,
included numerous forms from the Southern States, and not a few of the
more showy species from the Pacific Coast.
In some cases only half of the insect is shown. “Half a loaf is better
than no bread.” In some cases only one side of the wings is delineated.
Usually this is sufficient for identification. The inhabitants of this
earth have never seen but one side of the moon, but they know it when
they see it, unless they be like the tipsy pair, one of whom said to
the other, who was leaning against a lamp post, “Friend, is that the
moon, or a lamp?” and who received the reply: “Don’t ask me, I’m a
stranger myself in these parts.” By showing only one half, or one side,
of a species I have been able to illustrate many more than I could
otherwise have done.
The figures of some of the larger species have been slightly reduced to
accommodate them to the page, but as the natural size is always given
in the description the student need not be perplexed.
The author hopes that his readers will have as much pleasure in
studying the winged fairies of the woods and the fields as he has had
in preparing this small pocket guide for their assistance.
INTRODUCTORY
THE PLACE OF BUTTERFLIES IN THE ANIMAL KINGDOM
The Animal Kingdom is divided into various _subkingdoms_. One of these
is the subkingdom of the _Arthropoda_. This word is derived from the
Greek nouns ἄρθρον (_arthron_) meaning _joint_, and πούς (_pous_)
meaning _foot_. The _Arthropoda_ are animals the bodies of which are
made up of a series of rings or segments jointed together, and the
other organs of which are likewise composed of tubular bodies similarly
united. All arthropods are _invertebrates_; that is to say, they do not
have backbones and internal skeletons, such as are possessed by fishes,
reptiles, birds, and mammals, including man. Vertebrate animals have
_endoskeletons_, “inside skeletons.” In a ham, for instance, the bone
is internal to the muscular parts, or meat, and lies near the middle.
The muscles of a man clothe his bones. In the arthropods, on the
contrary, the hard parts clothe the muscles. Arthropods are therefore
said to have _exoskeletons_, “outside skeletons.” The body, the legs,
and other organs of an insect or a crab consist of a series of hollow
tubes held together by flexible skin at the points of union, and
controlled in their movements by muscles which pull from the inside.
The meat of a lobster is inside of the shell, or exoskeleton, as
everybody who has eaten a lobster knows. The arrangement is exactly the
reverse of that which we find in the vertebrates.
EXPLANATION OF PLATE A
Fig. a. _Magnified scales of butterflies._ 1, ordinary scale of
_Papilio_; 2, do. of _Colias_; 3 _androconium_, or scale from wing of
male _Neonympha eurytus_; 4, do. of male _Pieris oleracea_; 5, do. of
male _Lycæna pseudargiolus_ (Figs. 1-2 after Verity; Figs. 3-5 after
Scudder).
Fig. b. Patch of scales on wing of _Pieris napi_ (after Verity).
Fig. c. Body of _Anosia plexippus_.
I. Head. 1, antenna; 2, eye; 3, proboscis; 4, palpus; cl.
clypeus; o, occiput.
II. Thorax. 5, prothoracic leg; 6, mesothoracic leg; 7,
metathoracic leg; e, e, e, episterna; c, c, c, coxæ; tr.,
tr., trochanters of last two legs; f, f, femora of do.; s,
s, s, scuta of first, second, and third segments of thorax.
III. Abdomen. 1-9 segments; sp., sp., spiracles (after
Burgess).
Fig. d. Head and legs of _Œneis semidea_, showing aborted front leg.
Fig. e. Palpus of _Argynnis aphrodite_.
Fig. f. Leg of _Argynnis idalia_. 1, coxa; 2, trochanter; 3, femur;
4, tibia; 5, tarsus.
Fig. g. Knobbed antenna of _Argynnis idalia_.
Fig. h. Clubbed antenna of _Basilarchia astyanax_.
Fig. i. Hooked antenna of _Amblyscirtes vialis_.
[Illustration: PLATE A]
The subkingdom of the _Arthropoda_ is divided into six _classes_,
one of which consists of the _Insecta_ (insects). It is estimated
that there are three and a half millions of species of insects upon
the globe, not to speak of the vast number of species which are now
extinct, and known only by their fossil remains.
The Class _Insecta_ is subdivided into many _Orders_. To attempt even
to briefly speak of all these orders would take more space than the
publisher has allotted to the author, and it is enough to say that
butterflies belong to the order _Lepidoptera_. The lepidoptera are
divided into two _Suborders_: the _Rhopalocera_, or Butterflies, and
the _Heterocera_, or Moths. Both are characterized by having scaly
wings, hence the name, which is derived from the Greek words λεπὶς
(_lepis_) meaning _scale_, and πτερὸν (_pteron_) meaning _wing_.
Lepidoptera are “scale-winged insects.” Any one who has ever handled
a butterfly or moth, must have noticed upon his fingers a dust-like
substance, rubbed off from the wings of the captured insect. Upon
examining this substance under a microscope it is seen to be composed
of minute scales (see Plate A, Fig. _a_), and upon looking at the wing
of a butterfly under a magnifying glass it is seen to be covered with
such scales, arranged somewhat as the scales upon the sides of a fish,
or as the shingles upon the roof of a house (see Plate A, Fig. _b_).
Butterflies are mainly diurnal in their habits, preferring the
sunshine. Moths on the other hand are nocturnal, and fly in the
dusk, or after dark. Butterflies are therefore often called _diurnal
lepidoptera_, and moths are spoken of as _nocturnal lepidoptera_. There
are, however, a few butterflies which fly at dusk, and there are many
moths which are diurnal in their habits. Such moths are generally gay
in color, and for the most part inhabit tropical countries, although
we have a few such species in the United States. Ordinarily the best
way to distinguish between butterflies and moths is by examining their
antennæ, or “feelers,” as they are sometimes incorrectly called. In the
case of butterflies the antennæ are thread-like, terminating in a small
_knob-like_, or _club-like_ enlargement. It is this fact which has led
naturalists to call them _Rhopalocera_. The word is derived from the
Greek nouns ῥώπαλον (_rhopalon_) meaning a _club_, and κέρας (_keras_)
a _horn_. _Butterflies are lepidoptera having at the end of their
antennæ clubs, which are sometimes short, long, or hooked_ (see Plate
A, Figs. _g_, _h_, _i_.) The forms assumed by the antennæ of moths are
very various. The moths are therefore known as _Heterocera_, the word
being compounded from the Greek adjective ἕτερος (_all sorts_) and the
noun κέρας (_keras_) a _horn_. _Moths are lepidoptera having all sorts
of antennæ, except such as are club-shaped at their ends._ However
there is no rule without its exceptions, and there are a few rare moths
in tropical lands which have club-shaped antennæ like butterflies, but
none of these occur in the region with which this book deals.
THE ANATOMY OF BUTTERFLIES
The body of a butterfly consists of the head, the thorax, and the
abdomen (see Plate A, Fig. _c_).
The head carries two relatively large eyes, one on either side. The
eyes of insects are compound, and if examined under a microscope are
seen to have a multitude of minute facets, which serve to gather the
light from all directions, so that butterflies can look forward and
backward, upward and downward, as well as outward, all at one time.
Between the eyes on the upper part of the head arise the antennæ, of
which we have already spoken. The precise function of these organs in
insects has been the subject of much discussion. Supposed by some to
be ears, by others to be the seat of the sense of smell, by others to
combine within themselves these two senses, and by still others to
represent a sense which is not possessed by vertebrate animals, their
use in the life of insects is not yet clearly understood. The weight
of evidence seems to be in favor of the view that they are organs of
smell, and it is now quite firmly established by experiment that the
organs of hearing in insects are represented by certain pores and
openings on their legs. In front between the eyes and below the antennæ
are two little organs, each composed of three joints, which are known
as the _labial palpi_ (see Plate A, Fig. _e_). Between these, coiled up
like a watch-spring, is the proboscis, with which the butterfly sucks
up the nectar from flowers or drinks water from moist places (see Plate
A, Figs. _c_ and _d_). We have not the space in this little manual to
go more deeply into the anatomy of these organs, but enough has been
said to enable the beginner to recognize the various parts. The student
realizes that the head in general supports the principal organs of
sense and the proboscis, or mouth.
The thorax carries the organs of locomotion, which consist of four
wings and six feet. The thorax is made up of three segments, or
rings, the foremost of which is called the _prothorax_, the next the
_mesothorax_, and the hindmost the _metathorax_. The subdivisions of
the thorax are not easily distinguishable by examining the body of a
butterfly even under a microscope, because the bodies of butterflies
are generally heavily clothed with hairs and scales. In order to
clearly make out the subdivisions, which we are considering, it is
necessary to take a specimen and denude it of its scales and hairs,
and even dissect it under a glass. The correctness of the foregoing
statements then becomes apparent.
The legs of butterflies are arranged in three pairs, the foremost of
which are known as _prothoracic_, being attached to the prothorax;
the second pair are called _mesothoracic_, springing, as they do,
from the middle segment of the thorax; and the last are styled
_metathoracic_ legs, rising from the hindmost segment of the chest
(see Plate A, Fig. _c_). It should be noted here that in the great
family of the _Nymphalidæ_, or “Brush-footed Butterflies,” in both
sexes the anterior, or prothoracic pair of legs, are not fully
developed, being aborted (see Plate A, Fig. _d_) and therefore do not
serve for walking; and that in the families of the _Erycinidæ_, or
“Metal-marks,” and the _Lycænidæ_, or “Blues and Coppers,” the females
have six legs adapted to walking, while the males possess only four
ambulatory legs, the front pair being in the latter sex aborted in
these families, as in the _Nymphalidæ_. The legs of butterflies, like
those of all other insects, consist of five parts (see Plate A, Fig.
_f_) the first of which, nearest the body, is called the _coxa_, with
which articulates a small ring-like piece, known as the _trochanter_.
To the trochanter is attached the _femur_, and united with the latter,
forming an angle with it, is the _tibia_. The last division of the
leg is the _tarsus_, or foot, composed of a series of joints, to the
last of which is attached a pair of claws, which in butterflies are
generally rather minute, though in other orders of insects these claws
are sometimes long and powerful, this being especially true of some
beetles. The prothoracic legs of the _Nymphalidæ_ and of the males of
the _Erycinidæ_ and _Lycænidæ_ have lost the use of the tarsus, only
retaining it in feeble form, and the tibia has undergone modification.
In many of the _Nymphalidæ_ the tibia is densely clothed with long
hairs, giving this part of the leg the appearance of a brush, whence
the name “Brush-footed Butterflies” (see Plate A, Fig. _d_). The tibiæ
are often armed with more or less strongly developed spines.
The most striking parts of butterflies are their wings, which in
proportion to the size of their bodies are usually very large, and
which are remarkable for the beauty of the colors and the markings
which they display both on the upper and on the under side.
The wings consist of a framework of horny tubes which are in reality
double, the inner tube being filled with air, the outer tube with
blood. The blood of insects is not, like that of vertebrates, red in
color. It is almost colorless, or at most slightly stained with yellow.
The circulation of the blood in the outer wall of the wing-tubes
takes place most freely during the brief period in which the insect
is expanding its wings after emergence from the chrysalis, concerning
which we shall have more to say elsewhere. After the wings of the
butterfly have become fully expanded, the circulation of the blood in
the wings ceases almost entirely. The horny tubes, which compose the
framework of the wings of butterflies, support between them a delicate
membrane, to which upon both the upper and lower sides are attached
the scales. The two fore wings are more or less triangular in outline;
the hind wings are also subtriangular, but are generally more or less
rounded on the outer margin, and in numerous forms are provided with
tails or tail-like prolongations.
Inasmuch as in describing butterflies authors generally devote a good
deal of attention to the markings of the wings, it is important for the
student to become acquainted with the terms employed in designating
the different parts of the wings (see Plate B, Fig. 10). That part
of the wing which is nearest to the thorax, is called the _base_; the
middle third of the wing is known as the _median_ or _discal area_; the
outer third as the _external_ or _limbal area_. The anterior margin
of the wing is called the _costal margin_; the outer edge is styled
the _external margin_; the inner edge is known as the _inner margin_.
The tip of the front wing is called the _apex_, which may be rounded,
acute, falcate (sickle-shaped), or square (see Plate B, Figs. 1-4).
The angle formed by the outer margin of the front wing with the inner
margin is commonly known as the _outer angle_. The corresponding angle
on the hind wing is known as the _anal angle_, and the point of the
hind wing, which corresponds with the tip or apex of the fore wing,
is designated as the _external angle_. The margins of wings may have
different styles of outline, and are spoken of as entire, crenulate,
scalloped, waved, lobed, or tailed (see Plate B, Figs. 5-8).
A knowledge of the veins which form the framework of the wings is
important, because authors have frequently established genera upon
the basis of the wing structure. It is desirable on this account to
understand the nomenclature which has been applied to the veins. This
nomenclature is somewhat variant, different writers having employed
different terms to designate the same vein. In what follows the writer
has adopted the designations which are most current, and which are
generally accepted by authors. The best understanding of this matter
is to be derived from the attentive study of the diagrams given on
Plate B, Figs. 9 and 10. The veins in both the fore and hind wings
of butterflies may be divided into simple and compound veins. In
the fore wing the simple veins are the _costal_, the _radials_,
the _submedian_, and the _internal_; in the hind wing they are the
_costal_, the _subcostal_, the _radials_, the _submedian_, and the
_internal_. The costal vein in the hind wing is, however, generally
provided near the base with a short ascending branch, which is known as
the _precostal_ vein. In addition to the simple veins there are in the
fore wing two branching veins, one immediately following the costal,
known as the _subcostal_, and the other preceding the submedian, known
as the _median_. The branches of these compound veins are known as
_nervules_. The median vein always has three nervules. The nervules of
the subcostal veins branch upwardly and outwardly toward the costal
margin and the apex of the fore wing. There are always from four
to five _subcostal nervules_, variously arranged. In the hind wing
the subcostal is simple. The median vein in the hind wing has three
nervules, as in the fore wing. In both wings between the subcostal and
the median veins toward the base is enclosed the _cell_, which may be
either _closed_ or wholly or partially _open_ at its outer extremity.
The veinlets which close the cell are known as the discocellular veins,
of which there are normally three. From the point of union of these
_discocellular veins_ go forth the _radials_, known respectively as
_upper_ and _lower_, though the upper radial in many genera is emitted
from the lower margin of the subcostal vein.
EXPLANATION OF PLATE B
Fig. 1. _Angulated_ or _acuminate apex_ of fore wing (_Grapta_).
Fig. 2. _Falcate apex_ of fore wing (_Pyrrhanæa_).
Fig. 3. _Square apex_ of fore wing (_Smyrna_).
Fig. 4. _Rounded apex_ of fore wing (_Euptoieta_).
Fig. 5. Hind wing _rounded at outer angle, twice-tailed_ (_Thecla_).
Fig. 6. Hind wing _crenulate, tailed, lobed at anal angle_ (_Papilio_).
Fig. 7. Hind wing with _outer margin entire_ (_Parnassius_).
Fig. 8. Hind wing with _outer margin waved_ (_Argynnis_).
Fig. 9. Neuration of wings of _Anosia plexippus_.
_Veins_: C, costal; SC, subcostal; M, median; SM,
submedian; I, internal; PC, precostal; UDC, upper
discocellular; MDC, middle discocellular; LDC, lower
discocellular; UR, upper radial; LR, lower radial.
_Nervules_: SC 1, 2, 3, 4, 5, first to fifth subcostal
nervules; M 1, 2, 3, first to third median nervules.
Fig. 10. Wing of _Papilio turnus_, showing the names given to the
different parts of the wings of butterflies.
[Illustration: PLATE B]
Butterflies generally hold their wings erect when they are at rest,
with their upper surfaces facing each other, and only the under
surfaces displaying their colors to the eye. In the genus _Ageronia_
the insect prefers, like some moths, to settle upon the bark of trees,
with the wings spread flat, and the head pointing downward. Many of
the _Hesperiidæ_, or “Skippers,” have the habit when they are at rest
of holding the fore wings folded together, while the hind wings are
expanded horizontally. Many of the butterflies known as “Hair-streaks,”
belonging to the genus _Thecla_ and its allies, have the curious habit,
when at rest upon the end of a twig or leaf, of moving their folded
wings backward and forward, first on one side and then on the other,
thus partially displaying with each movement the splendid blue surfaces
of the upper side of the wings.
The abdomen of butterflies consists normally of nine segments (see
Plate A, Fig. _c_). In most butterflies except the Ithomiids, the end
of the abdomen does not extend beyond the anal angle of the hind wings.
In the moths, on the other hand, there are multitudes of genera in
which the extremity of the abdomen extends far beyond the hind margin
of the posterior wings. This is particularly true of the hawk-moths.
A minute examination of the abdomen of a butterfly reveals in each
segment except the last a little valve-like orifice on either side.
These openings are known as _spiracles_ (see Plate A, Fig. _c_).
Through these the insect breathes. Insects do not breathe through
their mouths, like vertebrates, and their lungs, or what correspond
to the lungs of the higher animals, are not located in the thorax or
chest, but in the abdomen. The last segment of the abdomen carries
at its extremity the external organs of generation. The male may be
distinguished from the female by the so-called _prehensores_, or
“claspers,” two flattish, scale-like appendages which adhere one on
either side to the last segment of the body. These organs are quite
peculiar in their structure, and in recent years have received a great
deal of study, as it has been found possible by means of them to
distinguish closely allied species, especially among the _Hesperiidæ_.
It is, however, not possible within our allotted space to go into a
minute discussion of this matter. The abdomen of the female is devoid
of these appendages, and in this sex is generally heavier and plumper,
especially when the eggs, which fill the ovaries, have not as yet been
deposited.
Thus far we have devoted our attention almost exclusively to the
consideration of the external organs of the suborder of insects which
is under discussion. It may be of interest to devote a few paragraphs
to the internal anatomy of butterflies. To do the subject full justice
would require a volume; nevertheless some general statements may pave
the way for a more studious inquiry on the part of readers.
Butterflies take their nourishment in fluid form, principally from the
cups which Flora provides. The organ of ingestion is the proboscis,
which communicates with a bulb-like receptacle in the head, known as
the pharyngeal sac, controlled by a set of muscles which cause it
to alternately expand and contract, very much like the bulb-syringe
used by physicians. When the muscles expand a vacuum is created, and
the fluid is drawn up from the honeyed chalice of the flower into the
receptacle in the head; when they contract, a valve in front closes, a
valve behind opens, and the honey in the receptacle is forced backward
through the œsophagus into the crop, and thence into the stomach.
The stomach lies on the ventral or under side of the body, but above
the nervous cord, which lies still more ventrad. The stomach opens
posteriorly into the small intestine, which is followed by the colon,
the latter in turn being succeeded by the rectum. Connected with the
intestines are certain vesicles, which are known as Malpighian vessels,
and by some are thought to have the function of the liver in higher
animals.
Having thus briefly spoken of the nutritive system we may turn to the
circulatory and respiratory systems. The heart of a butterfly, as in
all arthropods, lies on the dorsal side of the body. Its location
corresponds almost exactly to that occupied in the vertebrate animals
by the spinal cord. It is a long tubular organ. It does not possess
chambers—ventricles and auricles—such as are discovered in the heart
of vertebrates, but it has an enlargement in the mesothoracic region
known as the aortal chamber. The movement of the heart is wave-like,
analogous to the peristaltic movement in the intestines of the
vertebrates. From the heart there go out lateral blood-vessels, which
ramify and intermingle with the capillary extremities of the tracheæ,
or bronchial tubes, through which air is imported by way of the
spiracles, and thus the blood is purified in a manner quite analogous
to that in which the blood of the higher vertebrates is purified and
freed from waste matter by oxydization. The process is, however, as has
already been pointed out, mainly carried on in the abdominal region,
and not exclusively in the thorax, as in the case of vertebrates.
The nervous system of butterflies consists of a cord with _ganglia_, or
nerve-knots, one for each segment of the body. As there are thirteen
segments in the body of a butterfly, there are normally thirteen such
ganglia, or nerve centres. The nervous cord lies in a position exactly
opposite to that which is held by the spinal cord in vertebrates. It is
situated on the ventral side of the body, and more ventrad than all the
other internal organs. The ganglion in the head is the largest of all
and forms a rudimentary brain, the greater portion of which consists of
two relatively large optic nerves.
The internal organs of reproduction in the female consist of the
ovaries, from which the eggs pass by way of the oviduct to the
ovipositor, which in butterflies is not so conspicuous or remarkable
an organ as is the case in many other insects. Communicating with
the oviduct are the spermatothecæ, which are receptacles in which is
retained the fertilizing fluid received from the male at the time of
coition. As the eggs, one by one, are passed from the ovaries into the
oviduct, they are impregnated through absorption of the spermatozoa,
which enter their walls, imparting to them vitality. The internal
organs of the male are tubular vesicles, or testes, which secrete the
seminal fluid, which by means of the intromittent organ is introduced
into the spermatothecæ of the female. Union between the sexes among
insects generally takes place but once, and is not recurrent. The
female, having been impregnated, proceeds at once to lay her eggs upon
the tender leaves or the bark of the plants upon which her progeny
are to be nourished, and then promptly dies. The life of insects in
the winged form is usually very brief. Inasmuch as there are great
differences between the sexes in insects alike in size, form, color,
and markings, it is well for the collector to carefully preserve
specimens which may be captured in copulation. Such specimens should
be designated as “Taken _in coitu_.” The writer in such cases uses the
formula “A ♂ _in coitu_ with B ♀,” which is put in minute handwriting
upon a label and placed upon the pin bearing the male insect. Upon the
pin carrying the female insect there is put the label “B ♀ _in coitu_
with A ♂.” The finding of insects _in copula_ is sometimes the only
way in which to definitely settle the question of sexual relationship
between forms. So different are some insects that the two sexes have
in a number of cases been described by early writers as belonging
not merely to different species, but to different genera, and even
families.
THE LIFE HISTORY OF BUTTERFLIES
Almost all insects undergo great changes, or metamorphoses, during
their existence. Butterflies furnish no exception to this statement.
They exist first as _eggs_; then they appear as _caterpillars_; the
third stage is that of the _chrysalis_; the final stage is that of the
_imago_, or perfectly developed insect.
THE EGGS OF BUTTERFLIES
The eggs of butterflies are beautiful objects when examined under a
glass. They have various forms. Some are spheres or half spheres,
some are conical, cylindrical or spindle-shaped, others are flat and
resemble little cheeses, and still others have the form of turbans.
There is endless variety of form displayed within certain limits. Their
surfaces may be quite smooth or they may be adorned with raised ribs
and sculpturings (see Plate C, Figs. _f_ and _g_) or marked with little
pittings or depressions arranged in geometrical patterns. They vary
in color. Some are white, some pale green, or blue-green; others are
yellow, orange, red, or purple. They are often spotted and marbled like
the eggs of some birds.
The eggs of butterflies are deposited by the female upon the plants
which are appropriate to the development of the larvæ. Caterpillars are
very rarely promiscuous feeders, and most species are restricted to
certain species or genera of plants. Even when they feed upon different
plants, observation shows that, having begun to feed upon a certain
plant, they prefer this to all others, and do not willingly accept
anything else. I have noticed frequently that larvæ which may for
instance feed in nature upon the wild plum or the lilac, having begun
to feed upon the one will steadily refuse the other if offered to them.
On several occasions I have lost broods of caterpillars by attempting
to change their diet, though knowing well that the species is found
feeding in nature upon the plants which I have offered to them. Almost
every plant has a butterfly or moth which is partial to it, and one
of the most wonderful things in nature is the way in which the female
butterfly, without having received a botanical education, is able to
select the plant which will best meet the needs of her progeny, which
she never lives to see.
The eggs are deposited sometimes singly, sometimes in small clusters,
sometimes in a mass. Fertile eggs, soon after they have been laid,
undergo a change in color, and it is then possible with a magnifying
glass to see through the thin shell the form of the caterpillar which
is being developed within.
When the development is completed the caterpillar emerges either from
an opening at the side or at the top of the egg. Many species have eggs
provided with a sort of lid, a portion of the shell being separated
from the remainder by a thin section, which finally breaks under the
pressure of the enlarging embryo within, this portion flying off,
the rest adhering to the twig or leaf upon which it has been placed.
Many larvæ have the habit, as soon as they have emerged from the egg,
of making their first meal upon the shell from which they have just
escaped.
CATERPILLARS
The second stage in which the insects we are studying exist is known
as the _larval stage_. When it is reached the insect is spoken of as a
_larva_, or _caterpillar_ (see Plate C, Fig. _h_). Caterpillars have
long, worm-like bodies, which are often thickest about the middle,
tapering before and behind, and more or less flattened on the under
side. Sometimes caterpillars are oval or slug-shaped. Very frequently
their bodies are adorned with hairs, spines, and tubercles of various
forms. The body of the larva, like the body of the butterfly, consists
normally of thirteen rings or segments, of which the three foremost,
just behind the head, correspond to the prothorax, the mesothorax,
and the metathorax of the perfect insect, while the remaining nine
correspond to the abdomen of the imago. These three anterior segments
bear legs, which correspond to the legs of the winged form in their
location, and are known as the true legs of the larva. Besides these
the caterpillar has about the middle of the body and at its posterior
end paired _pro-legs_, as they are called, which are its principal
organs of locomotion in this stage, but which do not reappear in the
butterfly. The mouth parts of caterpillars are profoundly different
from those of the butterfly. The imago lives, as we have seen, upon
fluid nourishment, and therefore is provided with a sucking organ, the
proboscis. The caterpillar, on the other hand, is armed with a pair of
cutting mandibles, with which it shears off tiny strips of the leaves
upon which it feeds. It holds the edge of the leaf in place with the
three pairs of true legs, while it supports its body upon the pro-legs
during the act of eating.
EXPLANATION OF PLATE C
Fig. a. Caterpillar of _Anosia plexippus_ ready to change into a
chrysalis.
Fig. b. Do. after having partly shed its skin.
Fig. c. Do. holding itself suspended in the air by grasping the shed
skin between the edges of the third and fourth abdominal segments, and
feeling about with the cremaster for the button of silk above.
Fig. d. Do. after having caught the button and assumed its final form
as a chrysalis.
Fig. e. Chrysalis of _Papilio philenor_, held by button and girdle of
silk.
Fig. f. Egg of _Basilarchia disippus_, greatly magnified.
Fig. g. Egg of _Anosia plexippus_, greatly magnified.
Fig. h. Caterpillar of _Basilarchia disippus_.
(All the figures are after Riley.)
[Illustration: PLATE C]
When the caterpillar emerges from the egg the head is in many cases
seen to be very large in proportion to the rest of the body. This
relative disparity soon disappears, however, as growth takes place.
As the larva increases in size, it soon reaches a point at which the
skin in which it made its appearance in the world becomes too small and
tight for further comfort and use. Thereupon it proceeds to moult, or
shed, this now uncomfortable garment. The skin splits along the back
and the caterpillar crawls out of it. Before moulting the caterpillar
always takes the precaution to attach this outer skin by strands of
silk to the leaf or branch upon which the moult is to take place.
Having escaped from the cast-off garment, the caterpillar sometimes
turns around and eats it before resuming its vegetable diet. The
process of moulting takes place four or five times before the larva
changes into a chrysalis.
Caterpillars differ entirely from butterflies in that they are able
to produce silk. Silk is a viscous fluid secreted by elongated sacs
located in the dorsal region. These sacs communicate with a minute
tube-like organ, known as the spinneret, which is located on the under
side of the head of the caterpillar, just back of the mandibles. The
fluid silk, as it is ejected through the spinneret, immediately hardens
on contact with the air and is deposited in the form of very fine
threads or filaments which the caterpillar uses for various purposes,
sometimes as lines with which to guide itself from place to place
and enable it to retrace its steps to its favorite resting-place,
sometimes to tie together the leaves in which it forms its nest, or
to weave a sort of shelter in which it conceals itself, and finally
to make the little buttons and the girdles by which, as we shall see
later, the chrysalis is held in place. Many moths weave from silk
compact structures known as cocoons, in which the chrysalis is lodged.
Butterflies do not weave true cocoons.
The time spent by the insect in the egg is generally short. The time
passed in the larval state may be short or long. When butterflies
hibernate, or pass the winter, as caterpillars, the time spent in
this state is long, and especially in the case of those species which
inhabit arctic regions. There are some butterflies which occur north
of the Arctic Circle, and we have ascertained that these, because
the summers are so short in the far north, pass two summers and the
intervening winter in the larval condition, and another winter in the
pupal stage, before they emerge and take wing. On the other hand, under
more temperate conditions butterflies of certain species may produce
two or even three broods in a summer, and in subtropical or tropical
lands there may be even more broods produced.
While it is true that almost all the larvæ of lepidoptera subsist upon
vegetable food, there are nevertheless exceptions, one of which is that
of the Harvester, _Feniseca tarquinius_ (see Plate LXXXVIII, Fig. 1),
the slug-like larva of which feeds upon scale-insects, or mealy bugs,
sharing the habit with certain allied species which occur in Africa and
Asia, as the writer has had occasion to point out a number of years ago
in certain of his writings.
THE PUPA, OR CHRYSALIS
The third stage in the life of lepidoptera is known as the pupal
stage. The caterpillar, having undergone successive moults and reached
maturity, is transformed into a pupa, or chrysalis (see Plate C,
Figs. _d_ and _e_). From having been an active, worm-like creature,
greedily feeding upon its appropriate food, it reverts to a form
which is stationary, as was the egg, and ceases to have the power of
locomotion. An examination of the structure of all chrysalids shows
that they contain an immature butterfly. The segments of the chrysalids
enclose the corresponding segments of the body of the butterfly, and in
sheathing plates of chitinous matter are enfolded the wings and all the
other organs which are necessary to the life of the butterfly when it
shall have emerged and taken wing. The act of transformation from the
caterpillar stage to the pupal stage is very wonderful. The caterpillar
makes provision for the great change by weaving a little button of silk
and, in the case of many of those larvæ, the chrysalids of which are
not pendant, by also weaving a little girdle of silk, which it passes
around its back, and which holds it in place very much as an Indian
baby is held by the strap which passes over the shoulders of the squaw
(see Plate C, Fig. _e_). Having made these preliminary arrangements the
caterpillar becomes very quiet, its hind pro-legs being securely hooked
and tangled into the silken button to which it is attached. After a
while, when the proper moment has arrived, the skin of the caterpillar
splits, just as in the moults which preceded, and by a series of
wriggling or vibratory motions the chrysalis succeeds in working off
the skin of the caterpillar until it has all been shed except where
near the end of the abdomen the skin is caught between the edges of
two of the horny rings which form the abdomen. Then the insect with
the _cremaster_, as it is called, a little spikelet at the very tip of
the chrysalis, which is armed with small hooks, proceeds to feel about
until these hooks become entangled in the silk of the button which has
been provided on the under surface of the twig, the stone, or the fence
rail, where the transformation is occurring. As soon as the chrysalis
is securely hooked into the button of silk it lets go of the little
section of the skin by which it has been supported and rapidly assumes
the shape in which it will remain until the time of its emergence as a
butterfly. These changes are illustrated on Plate C, Figs. _a-d_, which
are reproduced from “The Butterfly Book” after the drawings of the late
Prof. C. V. Riley. The chrysalids of all the Nymphalidæ are pendant;
those of the other families, except the Hesperiidæ, are provided with
girdles, as is shown on Plate C, in the figures which represent the
chrysalis of _Papilio philenor_. The chrysalids of the Hesperiidæ, like
the chrysalids of moths, are either formed in loosely woven coverings
of leaves tacked together with silken threads, or lie free under leaves
and rubbish upon the ground, thus resembling the chrysalids of moths.
Chrysalids are for the most part rather obscure in coloring, though
some are quite brilliantly marked with metallic spots as in the case
of the common Milkweed Butterfly, _Anosia plexippus_, the chrysalis of
which is pearly green in color, ornamented with bright golden spots.
The forms assumed by chrysalids are very various, especially among the
Nymphalidæ, and they are often ornamented with curious projections and
tubercles, imparting to them very odd outlines.
Some butterflies remain in the chrysalis stage for only a few days or
weeks; others pass the winter in this state, and this is true of many
of the species which are found in the colder parts of North America.
In temperate regions some butterflies have as many as three broods:
the spring brood, which comes forth from chrysalids which have
over-wintered, an early summer brood, and a fall brood. In tropical
countries many species retain the form of the chrysalis during the dry
season, and emerge upon the wing at the beginning of the rainy season,
when vegetation is refreshed and new and tender growths take place in
the forests.
THE IMAGO, OR WINGED INSECT
We have already spoken at length of the form and structure of
butterflies in the preceding paragraphs, which were devoted to the
anatomy of butterflies. It remains for us at this point to call
attention to the manner in which the butterfly undergoes transformation
from the chrysalis. This change is quite as interesting as that
which takes place when the caterpillar is transformed into the pupa;
and should any of my readers possess chrysalids I would advise them
to watch carefully and observe the curious events which follow one
another rapidly when the imago comes forth from the cerements of the
chrysalis. The coverings which ensheathe the head, the legs, and the
antennæ split, the head protrudes, the fore legs are disentangled and
are thrown forth, followed almost at once by the other legs, and the
insect proceeds to crawl out from the pupal skin, emerging with the
wings as miniature objects, the body trailing after as a long worm-like
mass. Having liberated itself from the sheathings of the chrysalis, the
insect immediately assumes a stationary position, head upward, body
hanging downward. Then by the action of the heart the fluids which fill
the body begin to be rapidly sent into circulation, more particularly
into the wings, which expand second after second, minute after minute,
the fluids in the body being transferred through the circulatory system
of the wings until the latter, hanging downward, have assumed their
full form. The insect then begins gently to move its wings, to fan
them, still remaining in the position which it first took. After a
while the wings become perfectly dry, and the long worm-like body has
shrunk up and has assumed the form which it will retain through the
subsequent life of the insect. Madame Butterfly then begins to change
her position. She carefully crawls a few steps to try her powers of
locomotion. She suddenly expands her wings, and, _presto!_ if you alarm
her, she is off, fluttering about the cage in which you may have her,
or darting forth into the room and through the open window, hieing
herself forth in quest of food, which awaits her in the honeyed cups of
the wild flowers.
EXPLANATION OF PLATE D
Fig. 1. Illustration showing the way to disable a butterfly in the net
by gently pinching the body where the wings come together.
Fig. 2. A butterfly net.
Fig. 3. _a_, hoop made of wire, the shanks tied together; _b_,
ferrule, plugged at _c_ with a piece of cork; the shanks having been
put into the top of the ferrule, melted solder is poured into the top,
and a good net-ring is made.
Fig. 4. Piece of paper used to cover cyanide at bottom of jar.
Fig. 5. Collecting jar, with lumps of cyanide and sawdust at bottom,
covered by paper, as shown in Fig. 4.
Fig. 6. Expanding block, used to expand and mount insects, the wings
of which have a tendency to droop or sink down.
Fig. 7. Expanding block, used to mount insects, the wings of which
have a tendency to rise up or close.
[Illustration: PLATE D]
COLLECTING BUTTERFLIES
In collecting butterflies the first thing is to get a net of some kind
with which to catch the insects without tearing their delicate wings,
and thus robbing them of their beauty (see Plate D, Figs. 1 and 2).
When I was a boy I made my own nets. I took a stick of tough wood
about four feet long, which was to serve as the handle. About seven or
eight inches from the upper end I wrapped it with copper wire; fishing
line will do as well. Then I split the stick down to the band I had
made around it. I then with my knife trimmed the two split portions
on their inner sides, so that they might be more flexible. I then
fashioned out of a piece of good green hickory (the white outer wood
must be used) a bow or hoop about twelve inches wide at its widest
part, and fitting this between the split ends of the stick put in a
wedge at the bottom of the cleft to keep the split ends well apart
and tied it neatly and securely in place. Upon the frame made in
this way I put a covering of green mosquito netting in the form of
a long bag. Many a fine insect I captured with this simple device,
which called only for a good jack-knife, a little ingenuity, ordinary
skill in whittling, and a supply of stout string. The cheapest and
simplest way to make the frame for a net is to take a long piece of
brass, aluminium, or galvanized iron wire about an eighth of an inch
in diameter and bend it into a circle, leaving two short shanks at the
end. Then fit the shanks into the top of the ferrule of a fishing-rod
plugged in the middle with a thin piece of cork or with clay, and pour
in melted solder. Plate D, Fig. 3 shows how the “trick” is done.
There are many devices for making frames for folding nets, and there
are a number of dealers in the United States who supply such nets at
moderate prices. The material for the bag of the net ought to be of
light stuff, and I prefer to use tarletan, preferably green in color,
or bobbinet. The latter is more durable though somewhat heavier than
tarletan. The bag of the net ought to be about three times as long as
the diameter of the ring upon which it is placed. It is well, after
the net has been sewed upon the ring, to cover it with a band of stout
dark-colored muslin, as otherwise the edge of the bag surrounding the
ring is apt to become speedily worn and torn.
The collector having provided himself with a net for capturing insects
must also provide himself with one or more collecting jars. It is
well to have several of these of a size convenient for carrying in
the pockets. For large specimens a larger jar is required; for small
specimens a smaller receptacle is better. The larger jar should
have the mouth about two and one half or three inches in diameter.
Wide-mouthed glass phials an inch and a half in diameter serve best
for the smaller receptacles. The stopper of the larger jar should be
of ground glass, of the smaller jar of good cork. Jelly tumblers or
glasses with tin tops make good collecting jars. In preparing the
jar for use place a few lumps of cyanide of potash about the size of
a filbert at the bottom; then put in a little clean sawdust to keep
the pieces of cyanide from rattling about; over the lumps of cyanide
paste a sheet of strong white paper perforated with a multitude of
holes. In doing this the writer has resorted to a simple method, which
is explained in the diagram on Plate D, Fig. 4. A piece of paper is
placed under the jar and a circle the size of the inside of the jar is
traced upon it. Then a disk is cut out about three quarters of an inch
greater in diameter than the original circle. The paper is punctured
over the entire surface included within the inner line, and then with
scissors little gashes are made from the outer circumference inward,
so as to permit of folding the edge of the disk inwardly. A little gum
tragacanth, or paste, is then applied to these upturned edges, the disk
is then inserted into the jar and pasted securely over the cyanide
by means of the upturned flaps. A jar thus charged will last for a
long time if kept stoppered when not in use. Cyanide has a tendency
to liquefy in the presence of moisture, and it is well therefore to
take care to keep the jar closed when not in use. It must, however, be
borne in mind that the fumes of hydrocyanic acid (prussic acid), which
are active in producing the death of the insect, will not be given off
in sufficient volume unless there is a small amount of moisture in
the jar, and in very dry climates the writer has sometimes found it
necessary to moisten the bottom of the jar with a drop or two of water.
Jars also may be charged with lumps of carbonate of ammonia, but as
this substance bleaches the wings of insects, especially those which
are green in color, its use is not strongly recommended. Figure 5 on
Plate D shows a jar prepared for use.