The respiration of these larvæ is very singular. Their abdomen is terminated by appendages, which they open to allow the water to penetrate into the digestive tube, the sides of which are furnished with gills communicating with the tracheæ. The water, deprived of oxygen, is then thrown out, and the larva advances thus in the water by the recoil. It has no tufts of external lateral gills, which in the case of the _Ephemeræ_ do the duty of fins. The pupa already presents stumps of wings. To effect its metamorphosis it drags itself out of the water, where it has lived for nearly a year, climbs slowly to some neighbouring plant, and hangs itself there. Very soon the sun dries and hardens its skin, which all of a sudden becomes crisp, and cracks. The dragon-fly then sets free its head and its thorax, and its legs; its wings, still soft and wanting in vigour, gain strength by coming in contact with the air, and, after a few hours, they have attained their full development. Immediately the insect abandons, like a worn-out suit, the dull slimy skin which had covered it so long, and which still preserves its shape (Fig. 394), and dashes off in quest of prey. The _Libellulas_ are common all over the world. Their type is the _Libellula depressa_ (Fig. 395), very common in Europe. The male is brown, with the abdomen blue underneath; the female, of a sort of olive-yellow, bordered by yellow on the sides. Both have the abdomen broad and flattened. The _Æshna_, with a cylindrical abdomen, attains to the length of two and a half inches. Its flight is more rapid than that of the swallow. The _Calepteryx_ flies more slowly. The male is of a metallic blue, its diaphanous wings are traversed by a band of greenish blue; the female, of a bronzed green, has wings of a metallic green, with a yellowish mark on the edge. These insects rest on reeds, retaining their wings in a vertical position. [Illustration: Fig. 396.--Male Raphidia.] [Illustration: Fig. 397.--Larva of a Raphidia.] [Illustration: Fig. 398.--Pupa of a Raphidia.] [Illustration: Fig. 399.--Mantispa pagana.] The _Agrions_, which are of the same family, have the body white, brown, or green, and the eyes very prominent. They are more slim and graceful than the _Libellulas_, properly so called; their larva are very elongated. In the spring, one meets in the woods with insects having large heads and elongated thoraces. The females have a long auger, with which to deposit their eggs under the bark of trees, where their larvæ, which feed on insects, and twist themselves about like small serpents, live. The pupæ are also very active; they resemble the adults very much, and have the wings laid against the body. These insects, which are met with everywhere, but always in small numbers, are the _Raphidias_, which we see represented (Figs. 396, 397, 398) in the state of larva, pupa, and adult, and the _Mantispas_ (Fig. 399), one species of which is common in the south of Europe.