. Elementary textbook of economic zoology and entomology. Zoology; Insect pests. THE CLASSIFICATION OF INSECTS 157 breathe by means of delicate leaf-like tracheal gills on the sides of the abdomen, and when ready to change into adult condition, crawl up out of the water onto the bank or plant stems or float to the surface, and there quickly cast the nymphal cuticle and issue as winged imago. Some species molt again after having used their wings a little while. The May-flies often issue from rivers or lakes in enormous numbers in the summer, and form an annoying plague to house-boat dwellers or
. Elementary textbook of economic zoology and entomology. Zoology; Insect pests. THE CLASSIFICATION OF INSECTS 157 breathe by means of delicate leaf-like tracheal gills on the sides of the abdomen, and when ready to change into adult condition, crawl up out of the water onto the bank or plant stems or float to the surface, and there quickly cast the nymphal cuticle and issue as winged imago. Some species molt again after having used their wings a little while. The May-flies often issue from rivers or lakes in enormous numbers in the summer, and form an annoying plague to house-boat dwellers or summer cottagers simply by their too abundant presence. Their dead bodies falling on the surface of the water are sometimes driven by the wind on the shore in great windrows. Order Plecoptera.—'The Plecoptera, or stone-flies, are unfamiliar insects which, like the May-flies, hatch from eggs dropped into the water, and live an immature life of several months as flattened wingless nymphs crawling about at the bottom. Indeed, the stone-fly nymphs often live side by side with the young May-flies, but can usu- ally be distinguished from them by be- ing thicker and broader, and having tracheal gills not leaf-like but composed of separate filaments or tufts of such FIG. 70. — Young filaments rising from the thoracic seg- to"^).. of. sto"e-f?>'' from California. (Twice ments, one tuft just behind each leg. natural size.) They cannot live in stagnant water or foul streams. When ready to change to the winged adult condition the nymphs crawl out from the water, the cuticle splits along the back, and the winged fly issues. The adult flies have four rather large, membranous, many- veined wings, the hind ones being larger than the front ones. The mouth-parts are well developed and fitted for biting, but the food habits are not known. About 100 species occur in North America, among which there is none injurious to man. The young of many kinds furnish food for many fishes. An
Size: 1249px × 2000px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookaut, bookpublishernewyorkhholtandcompany, booksubjectzoology
