. A manual of zoology. Zoology. IV. INSECTA: HEXAPODA 415 anlagen of the wings as small folds in the chitinous coat of the meso- and metathorax; these increase with each successive molt, until, with the last, they become functional wings in size, form and motion. Inside of each wing pad (B, i and 2) there is the anlage of the wing of the next stage. Since the larva;, from lack of wings, are forced to live under dilTerent conditions from the adults, conditions which demand special structures, the differences between the larva; and the adults are emphasized by the presence of specific larval org
. A manual of zoology. Zoology. IV. INSECTA: HEXAPODA 415 anlagen of the wings as small folds in the chitinous coat of the meso- and metathorax; these increase with each successive molt, until, with the last, they become functional wings in size, form and motion. Inside of each wing pad (B, i and 2) there is the anlage of the wing of the next stage. Since the larva;, from lack of wings, are forced to live under dilTerent conditions from the adults, conditions which demand special structures, the differences between the larva; and the adults are emphasized by the presence of specific larval organs. Thus the aquatic larv;e of dragon- flies and Mayflies, are distinguished, not only by the absence of wings, but by different form, different shaped mouth parts, and especially by the tracheal gills (fig. 452), usually lost at the last molt. Increase in larval characters leads to complete metamorphosis. In order to profit as much as possiljle by its adaptation to its environment the larva retains its shape as long as possible; the gradual change to the adult is suppressed and the alteration in form is postponed until the end of the larval life, to the period between the last two molts. In this inter- val there is such an energetic transformation of the organism that ordi- nary vital functions, especially motion and feeding, are interfered with or rendered impossible. This last stage therefore becomes a period of rest. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Hertwig, Richard, 1850-1937; Kingsley, J. S. (John Sterling), 1854-1929, ed. and tr. New York, H. Holt
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
