Pupæ after Goedart.
Curious Pupæ. From Madame Merian's work on the Insects of Surinam.
As in the case of the larva, so with the pupa; if it is found in a dark situation, it will probably be destitute of colour, or, at any rate, it will only be of a yellowish white: such pupæ, when taken out of their natural hiding-place, and exposed to the sunlight, become of a dark colour. Indeed the majority of pupæ are without any of the gay colouring which distinguishes the previous condition of the insect. It seems as if it had been thought unnecessary to deck in gorgeous raiment the cerements of what we might call "the tomb" of the insect. But there are some beautiful exceptions to this rule. The pupæ of most butterflies, which are suspended in open day, are of a green or yellowish brown colour. Some, however, are painted in fairer colours; and a still greater number are speckled with glittering spots of golden hue, and shine as though gilded with the purest leaves of that precious metal, and burnished. Hence, as before explained, the Latin and Greek terms of aurelia and chrysalis for the pupæ of these insects. The gilding makes them very attractive objects, being applied now in streaks, now in spots, and occasionally,—and this in the very common pupa of the butterfly whose caterpillar, or larva, feeds on the nettle,—they are entirely covered with this splendid coat. The shade of gilding ranges in the depth of its tone from a very pale yellow to the full lustre of virgin gold. No wonder that those who mistook the object of chemistry, in trying to turn all things into gold, were attracted by these glittering things, and actually believed these spots to be of real gold, and hence imagined that they had found out an argument in nature for the transmutation of common metals into that coveted one. But a little experiment, which it is in the power of any one to perform, would soon have undeceived them, and taught them the truth of the proverb, "All is not gold that glitters." By infusing a portion of saffron in hot water, and straining it off after a little time, and adding to the rich yellow liquor thus obtained a few lumps of pure gum Arabic, a sort of gilding varnish will be obtained, which, if applied to a bright shilling, will give it very much of a golden appearance, owing to the shining of the metal showing through a transparent film of a golden colour. The gilded look of the pupa was found by Réaumur to be produced in the same way by the shining white membrane of the inner skin showing through the outer skin, which is of a transparent yellow.
In the Transactions of the Linnæan Society for 1833, the Rev. L. Guilding describes a very curious pupa, the case of which resembles pearl. These little bodies are found in abundance in the island of Antigua, and are often sent home to Europe, under the name of "ground-pearl," as distinguished from the ordinary fishery-pearl. They are devoured by turkeys, and fowls, until the birds are nearly choked with them, when the remedy is to pour vinegar down the throat, which dissolves the pearls, and sets the poor bird at ease. They are strung into necklaces and purses by the ladies of the Bahamas. They long caused much perplexity to naturalists; but they were ultimately found to be really only the pupæ of a little insect which appears to infest the ants, those voracious creatures, and thus to keep down their numbers. A representation of the ground-pearl, and the insect within, is annexed.
Ground Pearl. The Insect and its Case magnified.