INTRODUCTION

CHAPTER I

THE LIFE-HISTORY AND ANATOMY OF BUTTERFLIES

"The study of butterflies,-creatures selected as the types of airiness and frivolity, -instead of being despised, will some day be valued as one of the most important branches of biological science."-BATES, Naturalist on the Amazons.

IN studying any subject, it is always well, if possible, to commence at the beginning; and in studying the life of animals, or of a group of animals, we should endeavor to obtain a clear idea at the outset of the manner in which they are developed. It is a familiar saying that "all life is from an egg." This statement is scientifically true in wide fields which come under the eye of the naturalist, and butterflies are no exception to the rule.

THE EGGS OF BUTTERFLIES

The eggs of butterflies consist of a membranous shell containing a fluid mass composed of the germ of the future cat

FIG. 1.-Egg of Basilarchia disippus, magnified 30 diameters (Riley).

form of a turban. at the ends.

erpillar and the liquid food which is
necessary for its maintenance and de-
velopment until it escapes from the
shell. The forms of these eggs are
various. Some are spherical, others
hemispherical, con-
ical, and cylindri-
cal. Some are bar-
rel-shaped; others
have the shape of
a cheese, and still
others have the

FIG. 2.-Egg of Basilarchia disippus, natural size,

at the end of under surface

of leaf (Riley).

Many of them are angled, some depressed Their surface is variously ornamented. Some

times they are ribbed, the ribs running from the center outwardly and downwardly along the sides like the meridian lines

FIG. 4.-Egg of Anosia plexippus, magnified 30 diameters (Riley).

variety in their

vations variously disposed. As there is great variety in the form of the eggs, so also there is great color. Brown, blue, green, red, and yellow eggs Occur. Greenish or greenish-white are common tints. The eggs are often ornamented with dots and lines of darker color. Species which are related to one another show their affinity even in the form of their eggs. At the upper end of the eggs of insects there are one or more curious structures, known as micropyles (little doors),

FIG. 5.-Egg of Anosia plexippus, natural size, on under side of leaf (Riley).

through which the spermatozoa of the male find ingress and they are fertilized. These can only be seen under a good micro

scope.

The eggs are laid upon the food-plant upon which the cater

pillar, after it is hatched, is destined to live, and the female re

veals wonderful

FIG. 9.-Upper end of egg of Pieris oleracea, greatly magnified, showing the micropyle.

instinct in selecting plants which
appropriate to the develop-
ment of the larva. As a

rule, the larvæ are restricted in
the range of their food-plants to
certain genera, or families of
plants.

are deposited

The eggs
sometimes singly, sometimes

are

FIG. 10.-Eggs of Grapta comma, laid in string-like clus

ters on the under side of

in small clusters, sometimes leaf. (Magniin a mass. Fertile eggs, a few fied.)

days after they have been deposited, frequently undergo a change of color, and it is often possible with a magnifying-glass to see through the thin shell the form of the minute caterpillar which is being developed within the egg. Unfruitful eggs generally shrivel and dry up after the lapse of a short time.

The period of time requisite for the development of the embryo in the egg varies. Many butterflies are single-brooded; others produce two or three generations during the summer in temperate climates, and even more generations in subtropical or tropical climates. In such cases an interval of only a few days, or weeks at the most, separates the time when the egg was deposited and the time when the larva is hatched. When the period of hatching, or emergence, has arrived, the little caterpillar cuts its way mass on a twig. forth from the egg through an opening made either

FIG. 11.-Eggs of Vanessa antiopa, laid in a

at the side or on the top. Many species have eggs which appear to be provided with a lid, a portion of the shell being separated from the remainder by a thin section, which, when the caterpillar has reached the full limit allowed by the egg, breaks under the pressure of the enlarging embryo within, one portion of the egg flying off, the remainder adhering to the leaf or twig upon which it has been deposited.

CATERPILLARS

Structure, Form, Color, etc.-The second stage in which the insects we are studying exist is known as the larval stage. The insect is known as a larva, or a caterpillar. In general cater

pillars have long, worm-like bodies. Frequently they are thickest about the middle, tapering before and behind, flat

tened on the under side. While the cylindrical shape is most common, there are some families in which the larvæ are short, oval, or slug-shaped, sometimes curiously modified by ridges and prominences. The body of the larvæ of lepidoptera consists normally of thirteen rings, or segments, the first constituting the head.

The head is always conspicuous, composed of horny or chitinous material, but varying exceedingly in form and size. It is very rarely small and retracted. It is generally large, hemispherical, conical, or bilobed. In some families it is ornamented by horn-like projections. On the lower side are the mouth-parts, consisting of the upper lip, the mandibles, the antennæ, or feelers, the under lip, the maxillæ, and two sets of palpi, known as the maxillary and the labial palpi. In many genera the labium, or under lip, is provided with a short, horny projection known as the spinneret, through which the silk secreted by the cater

pillar is passed. On either side,

FIG. 13.-Head of caterpillar of Papilio aste

rias, front view, enlarged.

just above the man-
dibles, are located the
eyes, or ocelli, which
in the caterpillar are
simple, round, shining
prominences, generally
only to be clearly dis-
tinguished by the aid
of a magnifying-glass.
These ocelli are fre-

FIG. 14.-Head of caterpillar of Anosia plexippus, lower side, magnified 10 diameters: 1b, labrum, or upper lip; md, mandibles; mx, maxilla, with two palpi; Im, labium, or lower lip,

with one pair of palpi; s, spinneret; a, antenna; o, ocelli. (After Burgess.)

quently arranged in series on each side. The palpi are organs of touch connected with the maxillæ and the labium, or under lip, and are used in the process of feeding, and also when the