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. [Illustration: _Ground Pearl. The Insect and its Case magnified._] CHAPTER III. RESPIRATION OF THE PUPA. Having glanced at these particulars in the history of the pupa, we come to the important question,--Does the pupa, in this torpid condition, still breathe, as the larva did, or not? On a careful examination we might detect, with the help of a magnifying glass, the same breathing holes or _spiracles_, spoken of on page 161, as appertaining to the larva; and were we sufficiently skilful to dissect the pupa, we should find much the same arrangement of air-tubes within the body. In the absence of all other means of ascertaining the fact, we should be warranted in concluding from the presence of these organs alone, that the pupa has the faculty of breathing, no less than the larva. M. Réaumur has given a beautiful description of the breathing-holes, or spiracles, of the pupa, and has represented them in an engraving, of which a copy is furnished at page 161. He found that they are protected by little valve-like contrivances, just as our mouths are protected by our lips; and these can be opened or closed at pleasure by the creature; so that if plunged into water, that fluid cannot enter the insect's body, for all its little doors--and there are no fewer than eighteen of them!--are fast shut. Singular to say, however, if plunged into oil, the oil has the power of entering them, and the pupæ may be thus drowned.