PUPA, CHRYSALIS, OR AURELIA.
THE words Aurelia or Chrysalis are equally used to express that inactive state which ensues after the Caterpillar has changed, for the great purpose of preparing for the Imago, or transformation to the Fly. Aurelia, is derived from the Latin aurum, and Chrysalis from the Greek, and are both intended to signify a creature formed of gold; this however is giving a general title, from a very partial circumstance, as the colour of a considerable number are black, or dark brown, while the resplendence of gold is only seen on the Chrysalides of a few species of the Papilio, or Butterfly. The term Chrysalis should therefore be used to signify only those of the Butter∣fly kind, and Pupa for the Phalaenae, or Moths, as well as those of Sphinxes, or Hawk Moths.
That very intelligent naturalist M. de Reaumur explains the cause of this brilliant appearance; it proceeds from two skins, the upper one a beautiful brown, which covers a highly-polished smooth white skin: the light reflected from the last, in passing through the upper∣most, communicates this bright golden yellow, in the same manner as this colour is often given to leather, so that the whole appears gilded, although no gold enters into that tincture.
The exterior part of the Pupa is at first exceedingly tender, soft, and partly transparent, being covered with a thick viscous sluid, but which drying forms a new covering for the animal.
The time each Insect remains in this state is very easily ascertained by those who once breed them, as they always remain the same space Page 18〈1 page duplicate〉Page 19〈1 page duplicate〉Page 20of time, unless forwarded or retarded by heat or cold, but in diffe∣rent species they vary considerably; for example, the Papilio Atalanta (Red Admirable) remained only twenty-one days in Chrysalis, from the 12th of July to the 3d of August, but the Phaloena Oo. (Heart Moth) remained from the beginning of October till May following; and many species remain a very considerable time longer than this.
When the Insect has acquired a suitable degree of solidity and strength, it endeavours to free itself from the case in which it is confined; and as it adheres to a very few parts of the body it does not require any great exertion to split the membrane which covers it; a small degree of motion, or a little inflation of the body is sufficient for the purpose; these motions reiterated a few times, enlarge the opening and afford more convenience for the Insect's escape; this opening is always formed a little above the trunk be∣tween the wings, and a small piece which covers the head. Those species which spin a cone, gnaw or pierce an aperture large enough for their emancipation.
The Moth immediately after emerging from its case is moist, with the wings very small, thick, and crumpled; but they rapidly expand under the eye of the observer, and in a few minutes have attained their full size; the moisture evaporates, the spots on the wings, which at first appeared confused, become distinct, and the fibres, which were before flexible, become stiff and hard as bones.
When the wings are unfolded, the antennae in motion, the tongue coiled up, the Moth fussiciently dried, and its different members strengthened, it is prepared for flight. The excrementitious dis∣charge which is voided by most Insects at this time M. de Reaumur thinks is the last they eject during their lives.