Before I tell you, I would have you more thoroughly acquainted with it. Continue your examination.
The face has a strange expression; it looks—the insect, I mean—like a masked knight. Its mask, formed of a scaly substance and thoroughly compact, is composed of two pieces, which are separated from one another by a transversal suture: the upper, which is broader than it is high, we may call the vizor; it consists of two lobes, soldered together longitudinally; the lower, which is higher than it is broad, will be the chin-piece; it is triangular in shape, and its base rests against the vizor, while the summit is jointed or articulated with a support, which acts as a hinge when the mask is raised or lowered.
These movements, let me tell you, are voluntary; the animal raises its mask to arrest on their way the Infusoria and other animalcules on which it feeds. For crushing them, it is provided with strong mandibles, which you can detect by lowering the mask with a pin, or the point of a penknife. The eyes, which resemble little mammillary protuberances, are situated above and outside of the vizor. On the animal's back, where the belly joins the thorax, do you observe those four little sheath-like or scabbard-like tongues? The extremity of the body, the tail, is marked by three conspicuous triangular points, lying close to the opening, through which the water enters and issues, as if it were alternately sucked in and poured out by a piston. This, you must understand, is the respiratory apparatus. (See Fig. 40.)
Fig. 40.—Larva of the Fig. 41.—Larva of Libellula depressa. the Agarion virgo.
Well, then, what is the name of this most singular creature, this masked knight?
It is the larva of the Libellula depressa; the dismal envelope whence will issue the gaudy Dragon-fly. Listen to a graphic description of the mask you are looking at:—
"Conceive your under-lip to be horny instead of fleshy, and to be elongated perpendicularly downwards, so as to wrap over your chin and extend to its bottom; that this elongation is there expanded into a triangular convex plate attached to it by a joint, so as to bend upwards again and fold over the face as high as the nose, concealing not only the chin and the first-mentioned elongation, but the mouth and part of the cheeks; conceive, moreover, that to the end of this last-mentioned plate are fixed two other convex ones, so broad as to cover the nose and temples; that these can open at pleasure transversely, like a pair of jaws, so as to expose the nose and mouth, and that their inner edges, where they meet, are cut into numerous short teeth, or spines, or armed with one or more sharp claws;—you will then have as accurate an idea as any powers of description can give you of the strange conformation of the under-lip of the larva of those insects, which conceals the mouth and face precisely as I have supposed a similar construction of your lip would do yours. When at rest, this mask applies closely to and covers the face; when they would make use of it, they unfold it like an arm, catch the prey at which they aim by means of the mandibuliform plates, and then partly refold it, so as to hold the prey to the mouth in the most convenient position for the operation of the two pairs of jaws with which they are provided."
And so the creature I have been examining is only a larva! How strange to compare it,—thick, ugly, unwieldy,—with the insect that issues from it, so aërial, so graceful, so light, so beautiful! The more I think of the contrast, the more it interests me.
This larva, however, has all the characteristics of a perfect insect, and I will wager that more than one observer has described it as such, and classified it among aquatic insects. Yet it is but a larva! And each species has its own special larva (see Figs. 40 and 41).