The Butterfly Book. W. J. Holland
the spots and colors on the wings of the insect.
Duration of Pupal Life.—Many butterflies remain in the chrysalis stage only for a few weeks; others hibernate in this state, and in temperate climates a great many butterflies pass the winter as chrysalids. Where, as is sometimes the case, there are two or three generations or broods of a species during the year, the life of one brood is generally longer than that of the others, because this brood is compelled to overwinter, or hibernate. There are a number of butterflies known in temperate North America which have three broods: a spring brood, emerging from chrysalids which have overwintered; an early summer brood; and a fall brood. The chrysalids in the latter two cases generally represent only a couple of weeks at most in the life of the insect. In tropical and semi-tropical countries many species remain in the chrysalis form during the dry season, and emerge at the beginning of the rains, when vegetation is refreshed and new and tender growths occur in the forests.
The Transformation from the Chrysalis to the Imago.—The perfectly developed insect is known technically as the imago. When the time of maturity in the chrysalis state has been reached, the coverings part in such a way as to allow of the escape of the perfect insect, which, as it comes forth, generally carries with it some suggestion of its caterpillar state in the lengthened abdomen, which it with apparent difficulty trails after it until it secures a hold upon some object from which it may depend while a process of development (which lasts generally a few hours) takes place preparatory to flight. The imago, as it first emerges, is provided with small, flaccid wings, which, together with all the organs of sense such as the antennæ, require for their complete development the injection into them of the vital fluids which, upon first emergence, are largely contained in the cavities of the thorax and abdomen. Hanging pendant on a projecting twig, or clinging to the side of a rock, the insect remains fanning its wings, while by the strong process of circulation a rapid injection of the blood into the wings and other organs takes place, accompanied by their expansion to normal proportions, in which they gradually attain to more or less rigidity. Hardly anything in the range of insect life is more interesting than this rapid development of the butterfly after its first emergence from the chrysalis. The body is robbed of its liquid contents in a large degree; the abdomen is shortened up; the chitinous rings which compose its external skeleton become set and hardened; the wings are expanded, and then the moment arrives when, on airy pinions, the creature that has lived a worm-like life for weeks and months, or which has been apparently sleeping the sleep of death in its cerements, soars aloft in the air, the companion of the sunlight and the breezes.
ANATOMY OF BUTTERFLIES
The body of the butterfly consists of three parts—the head, the thorax, and the abdomen.
The Head.—The head is globular, its breadth generally exceeding its length. The top is called the vertex; the anterior portion, corresponding in location to the human face, is called the front. Upon the sides of the head are situated the large compound eyes, between which are the antennæ, or "feelers," as they are sometimes called. Above the mouth is a smooth horny plate, the clypeus. The labrum, or upper lip, is quite small. On both sides of the mouth are rudimentary mandibles, which are microscopic objects. The true suctorial apparatus is formed by the maxillæ, which are produced in the form of semi-cylindrical tubes, which, being brought together and interlocking, form a complete tube, which is known as the proboscis, and which, when not in use, is curled up spirally, looking like a watch-spring. At the upper end of the proboscis, in the head, is a bulb-like enlargement, in the walls of which are inserted muscles which have their origin on the inner wall of the head. When these muscles contract, the bulb-like cavity is enlarged, a vacuum is produced, and the fluids in the cup of the flower flow up the proboscis and into the bulb. The bulb is also surrounded by muscles, which, when contracting, compress it. The external opening of the tube has a flap, or valve, which, when the bulb is compressed, closes and causes the fluid in it to flow backward into the gullet and the stomach. The arrangement is mechanically not unlike that in a bulb-syringe used by physicians. The process of feeding in the case of the butterfly is a process of pumping honeyed water out of the flowers into the stomach. The length of the proboscis varies; at its base and on either side are placed what are known as the maxillary palpi, which are very small. The lower lip, or labium, which is also almost obsolete in the butterflies, has on either side two organs known as the labial palpi, which consist of three joints. In the butterflies the labial palpi are generally well developed, though in some genera they are quite small. The antennæ of butterflies are always provided at the extremity with a club-shaped enlargement, and because of this clubbed form of the antennæ the entire group are known as the Rhopalocera, the word being compounded from the Greek word (ῥοπαλον), which means a club, and the word κεραζ (keras) which means a horn.
It will be observed from what has been said that the head in these creatures is to a large extent the seat of the organs of sense and alimentation. What the function of the antennæ may be is somewhat doubtful, the opinion of scientific men being divided. The latest researches would indicate that these organs, which have been regarded as the organs of smell and sometimes as the organs of hearing, have probably a compound function, possibly enabling the creature to hear, certainly to smell, but also, perhaps, being the seat of impressions which are not strictly like any which we receive through our senses.
Thorax.—The thorax is more or less oval in form, being somewhat flattened upon its upper surface. It is composed of three parts, or segments, closely united, which can only be distinguished from one another by a careful dissection. The anterior segment is known as the prothorax, the middle segment as the mesothorax, and the after segment as the metathorax. The legs are attached in pairs to these three subdivisions of the thorax, the anterior pair being therefore sometimes spoken of as the prothoracic legs, the second pair as the mesothoracic legs, and the latter