"Under these three forms are all the caterpillars of Libellas found, there being but little difference in the colours or marks of the respective tribes; the various sizes and shapes being the chief observable circumstances attending them. They are all furnished with six legs, and have each of them four little membranaceous substances issuing from the back, or upper part of the thorax, that are the follicles, or cases, wherein the wings are inclosed. When the young caterpillars issue from their confinement in the eggs, there is no appearance of these cases, nor till a considerable time after; but as they arrive to a maturer state they become more conspicuous, and, like the young leaves of trees that open {109}and expand themselves on the arrival of the spring, their appearance increases, till having approached the period when they are to forsake their former habitations and become inhabitants of the air, these wing-cases have then arrived to their due size, and carry the appearance in which they are here seen. They are all of them, from the largest to the smallest, armed with a strong offensive weapon, which serves them, and is indeed the means they are endued with, for obtaining their food. This weapon being placed in the under part of the head, just beneath the mouth, I have displayed in Fig. 1. and 3. of Plate 47. where it appears just in the same manner as when they are endeavouring to catch their prey. In the largest figure at 1. and also in Fig. 2. it appears contracted and shut up, as when at rest. The strength and power that these animals discover in the use of this instrument is very singular and extraordinary. There are two joints to it, one about the middle, the other underneath the mouth, close to the throat; and in some (particularly all those of Fig. 2.) when it is closed or contracted, it appears fastened to the face of the creature, by fitting it so exactly as to form a perfect mask; covering the mouth, and reaching almost as high as the eyes. In others it is made to fit only the under part of the mouth, and when at rest is drawn up close underneath it. At the extremity of those that are extended may be observed two very strong and remarkable fangs; that, shutting over each other, form a pair of forceps, of such strength that few, if any of their captives, can escape if once inclosed therein. [This organ is the greatly developed lower lip of the larva, and is analogous in its structure to the same part in the imago.]