. Bulletin of the Bureau of Fisheries. Fisheries; Fish culture. DRAGONFUES AND DAMSELFLIES IN PONDFISH CULTURE. 193 Imago.—In these latitudes the winter is passed in the nymph stage, and toward the close of the following spring the nymph, having passed through successive molts, is ready for transformation. This is accomplished by crawling out of the water onto some convenient object near at hand, to which it fastens with its claws. In a short time the skin splits across the top of the head and then along the back and the imago or perfect insect emerges, leaving the old nymph skin, called an ex
. Bulletin of the Bureau of Fisheries. Fisheries; Fish culture. DRAGONFUES AND DAMSELFLIES IN PONDFISH CULTURE. 193 Imago.—In these latitudes the winter is passed in the nymph stage, and toward the close of the following spring the nymph, having passed through successive molts, is ready for transformation. This is accomplished by crawling out of the water onto some convenient object near at hand, to which it fastens with its claws. In a short time the skin splits across the top of the head and then along the back and the imago or perfect insect emerges, leaving the old nymph skin, called an exuvia, fastened to its support. Teneral.—After emerging, the imago is of a uniform pale yellow or tinged with blue, brown, or white, and it takes from a few hours to several days for it to acquire the bright colors of the mature adult. During this time it is called a teneral, its body is soft and flabby, its wings shine as if varnished, and its powers of flight are quite Figs, i to 3.—The egg of Pachydiplax longipennis: i, newly laid; 2, three days old, dorsal view; 3, three days old, side view» showing at the right the large ventral plate and in the center the folded legs. Fig. 4.—Pronymph of Pachydiplax longipennis; length, mm. FlG. 5.—Nymph of Pachydiplax longipennis after the first moult; length, i mm. PruinosE.—After becoming thoroughly hardened, some species, especially the males, are gradually covered with a bluish or whitish powder which may hide entirely the original bright colors; they are then said to be pruinose. In Plathemis lydia the old males are almost white on the dorsal surface; in Erythemis and Pachydiplax they become blue; while in the damselfly, Argia puirida, the thorax and the last two segments of the abdomen appear to be blue, but this color disappears at once when they are put in alcohol. MOUTH PARTS OF ODONATE NYMPHS. Dragonfly Nymphs.—In dealing with the food of nymphs and adults we need to know a little about the means wh
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