Читать книгу The Butterflies of the British Isles - Richard South - Страница 9

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The term chrysalis more especially applies to such of them as are spotted or splashed with metallic colour, as, for example, the chrysalids of some of the Fritillaries. The scientific term for the chrysalis is pupa, which in the Latin tongue means "a doll or puppet."

Fig. 4.

Caterpillar of Small White, about to change to chrysalis.

In passing to the chrysalis stage the caterpillars have sometimes to make rather more preparations than in previous skin-changing provisions. Those of the Swallow-tail, Whites, Orange-tip, and similar kinds have to provide a silken girdle for the waist as well as a pad for the tail. Chrysalids that hang suspended, head downwards, such as the Vanessids, Fritillaries, etc., are attached by the cremaster—a hooked arrangement on the tail (Fig. 5)—to a pad of silk; others, such as the Blues and the Coppers, appear to be held in position on a leaf, or some other object, by means of a fine girdle of silk, or sometimes a few silken threads spread net-like above and below them—rudiments of a cocoon in fact. Chrysalids of the Skippers are enclosed in a more or less complete cocoon placed within a chamber, formed of a leaf or leaves of the food-plant, drawn together by silken cables. Some of these chrysalids are furnished with hooks on the tail as well as with a girdle for suspension; but others have hooks only.

Fig. 5.

Enlarged view of cremaster,

and a hook still more enlarged.

(After Sharp.)

As almost all the chrysalids here considered are figured in the illustrations, it will be unnecessary to refer in detail to their great diversity in form, but a few general remarks on the structure of a chrysalis may be made.

If the upper (dorsal) surface of a chrysalis is examined, the thorax and the body divisions will easily be made out, while, by looking at the sides and the under (ventral) surface, the various organs, such as the wings, legs, antennæ, etc., will be found neatly laid along each side of the "tongue," or proboscis, which latter extends down the centre. All these are separately encased, but by reason of the shell mentioned in the remarks on the caterpillar, they appear to be welded together. When, however, the butterfly is ready to emerge, the shell of the chrysalis is split along the thorax and at the lower edge of the wing-cases, and the insect is then able to release itself from the pupal trappings. This breaking open of the chrysalis shell is termed dehiscence (dehisco, "to split open"), and the manner in which it is effected varies in different species. The emergence of a butterfly from the chrysalis is always an interesting operation to observe, and every one should make a point of watching the process, so that he may obtain practical knowledge of how the thing is done. A photograph of it will be found in the description of the Wall Butterfly.