Entomology : with special reference to its biological and economic aspects . J ANATOMY AND PHYSIOLOGY 135 larvcTS of aquatic habit, as Gyriiiiis andCiiriiiidotiis, possess tracheal gihs, as doalso caterpillars of the genns Pavdponyx(Fig. 171), which feed on the leaves ofseveral kinds of water plants. Though manifold in form, trachealgills are generally more or less foliaceousor filamentous, presenting always an ex-tensive respiratory surface; their integu-ment is thin and the tracheae spreadclosely beneath it. These adaptationsare often supplemented by waving move-ments of the gills, as in May
Entomology : with special reference to its biological and economic aspects . J ANATOMY AND PHYSIOLOGY 135 larvcTS of aquatic habit, as Gyriiiiis andCiiriiiidotiis, possess tracheal gihs, as doalso caterpillars of the genns Pavdponyx(Fig. 171), which feed on the leaves ofseveral kinds of water plants. Though manifold in form, trachealgills are generally more or less foliaceousor filamentous, presenting always an ex-tensive respiratory surface; their integu-ment is thin and the tracheae spreadclosely beneath it. These adaptationsare often supplemented by waving move-ments of the gills, as in May fly nymphs,and by frequent movements of the insectfrom one place to another. Especially noteworthy are the rectaltracheal gills of odonate nymphs. Inthese insects the lining of the rectumforms numerous papill3e or lamellas, which Fig. Caterpillar of Para-ponyx obscuralis, to showtracheal gills. Length,15 mm.—After Hart. Fig. 172. Larva of Bittaco-morpha clavipcs, show-ing respiratory size. — AfterHart. contain a profusion of delicate trachealbranches; these are bathed by waterdrawn into the rectum and then expelled,at rather irregular intervals. A similarrectal respiration occurs also in ephemeridnymphs and mosquito larvae. A few forms, chiefly Perlidre, areexceptional in retaining tracheal gillsin the adult stage; in some imaginesthey are merely vestiges of the nymphalgills, but in others, such as Pteroiiarcys(Fig. 18), which ha])itually dips intothe water and rests in moist situations,the gills probably supplement the spira-cles. Further details on the respirationof aquatic insects are given in ChapterIV. 136 ENTOMOLOGY Spiracles.—The paired external openings of the tracheaeoccur on the sides of the thorax and abdomen, there beingnever more than one pair to a segment. Though the thysa-nuran Jap
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
