Identifier: entomologywit00fols (find matches)
Title: Entomology : with special reference to its biological and economic aspects
Year: 1906 (1900s)
Authors: Folsom, Justus Watson, 1871-1936
Subjects: Entomology
Publisher: Philadelphia : P. Blakiston's Son
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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Text Appearing Before Image:
Tracheal system of an insect, a, an-tenna; b, brain; /, leg; 11, nerve cord;p, palpus; s, spiracle; st, spiracular, orstigmatal, branch; t, main tracheal trunk;V, ventral branch; is, visceral branch.—After KoLBE. ANATOMY AND PHYSIOLOGY 133 9. Respiratory SystemIn insects, as contrasted with vertebrates, the air itself isconveyed to the remotest tissues by means of an elaborate sys-tem of branching air-tuljes, or iracJiccv, which receive airthrough paired segmentally-arranged spiracles. Each spiracleis commonly the mouth of a short tube which opens into amain tracheal trunk (Fig. 167) extending along the side of
Text Appearing After Image:
Diagrammatic cross section of the thorax of an insect, a, alimentarj canal; d,dorsal vessel; g, ganglion; s, spiracle; w, wing; /, dorsal tracheal branch; 3, visceralbranch; 3, ventral branch. the body. From the two main trunks branches are sent whichdivide and subdivide until they become extremelv delicatetubes, which penetrate even between muscle fibers, between theommatidia of the compound eyes and possibly enter cells. Inmost cases each main longitudinal trunk gives off in each seg-ment (Fig. 168) three large branches: (i) an upper, or dor-sal, branch, which goes to the dorsal muscles; (2) a middle,or visceral, branch, which supplies the alimentary tract and thereproductive organs; (3) a lower, or ventral, branch, whichpertains to the ventral ganglia and muscles. In many swiftly-flying insects (dragon flies, beetles, moths,flies and bees) there occur tracheal pockets, or air-sacs, which 134 ENTOMOLOGY Fig. 169. were formerly and erroneously supposed to diminish theweight of the in

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