Hagen also states that in the dragon-fly, Euphæa, the gills of the nymphs are retained in the imago, and Palmén remarks that in Æschna the rectal gills of the nymph persist in the imago, though not used for respiration.
Palmén gives an instance of a caddis-fly (Hydropsyche, Fig. 448) retaining its gills through the imago stage, but they are unfit for respiration, as they are minute and shrunken.
A walking-stick (Prisopus flabelliformis) found in the mountains of Brazil has the remarkable habit, according to Murray, of spending “the whole of the day under water, in a stream or rivulet, fixed firmly to a stone in the rapid part of the stream,” with its head turned up stream; but leaving the water at dark. The under side of the body, including the head, is hollowed so that the creature may adhere, sucker-like, to smooth stones; the claws, claspers, and flaps on the legs aid in retaining its hold, while the outer margin of the legs is dentate and thickly fringed with hair to repel the water.
Another form, closely related to Prisopus, from Borneo (Cotylosoma dipneusticum) is said by Wood-Mason to be even more profoundly modified for an aquatic life, since it has not only spiracles, but also, as he claims, tracheal gills. From each side of the body, in fact along the lower margins of the sides of the metathorax, there stand straight out five equal, small, but conspicuous ciliated oval plates, “which, when the insect is submerged and its stigmata are closed, doubtless serve for respiration.” The author did not note the actual presence of tracheæ in these plates.
LITERATURE ON THE ORGANS AND PHYSIOLOGY OF RESPIRATION
a. On the tracheal system in general
Lyonet, P. Traité anatomique de la chenille qui ronge le bois du saule. (La Haye, 1760; 2d edit., La Haye, 1762, pp. 616, 18 Pls.)
Treviranus, G. R. Beiträge zur Anatomie und Physiologie der Tiere und Pflanzen, 1816.
—— Das organische Leben. Bremen, 1831.
Rengger, J. R. Physiologische Untersuchungen über die tierische Haushaltung der Insekten. Tübingen, 1817. (Germar’s Mag. f. Ent., 1818, iii, pp. 410–413.)