File:Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct - for the use of schools and colleges (1870) (14596085559).jpg

Identifier: outlinesofcompar00agas (find matches)
Title: Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges
Year: 1870 (1870s)
Authors: Agassiz, Louis, 1807-1873 Gould, Augustus A. (Augustus Addison), 1805-1866 Wright, Thomas, 1809-1884
Subjects: Physiology, Comparative Zoology
Publisher: London : Bell & Daldy
Contributing Library: MBLWHOI Library
Digitizing Sponsor: MBLWHOI Library

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s,after a time, becomes the chry-salis, which finally developsthe perfect insect. The jaws ofinsects (figs. 195 to 199) areconstructed after the type wehave already described in an-nelida, Crustacea, and arach-nida, that is to say, they areplaced laterally, and moved bypowerful muscles; we recog-nize two pair, an external pair,or mandibulse (fig. 195, m\and an internal pair, or maxil-Ise (j); the mouth is furnishedwith a superior lip, or labrum,and an inferior lip, or labium.The development of the jawsis in strict relation with thenatural food of the insect. Thesuctorial apparatus of the hy-menoptera, that of the commonbee (fig. 1 9G), for example, isvery singular; projecting frombetween the jaws we observe asucker (/), composed of nume-rous rings ; this organ, calledby Treviranus the fleshytongue, is situated at the com-mencement of the esophagus,in a horny sheath, formed bya prolongation of the labise,into which it can be with-drawn at pleasure. The canalof the sucker is very incon-
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Fig. 179.—Digestive Organs of aBeetle. a, the head which supports thejaws; b, the crop and gizzard ; d,the chylific stomach; c, the biliaryvessels; d, the intestine; e, secretingorgans ; /, the anus. 176 ORGANS OF DIGESTION. siderable, opening into a bag situated before the esophagus,into which it leads ; the function of this bag appears, ac-cording to Burmeister, to be simply the rarefaction of itscontained air, by which fluids in the proboscis and esopha-gus are pumped up into the first stomach. Insects pro-vided with organs of mastication are deprived of this suck-ing apparatus; so that the development of maxillae and suc-torial instruments stand in an inverse ratio to one another.Burmeister is of opinion that, in insects deprived of a pro-boscis, the sucking bag is converted into a crop. Thedigestive organs of coleopterous insects present considerablevariety in their structure; two sections of the order areformed on this difference alone; to the one section belongsthose which ha

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