Entomology : with special reference to its biological and economic aspects . 44).Usually, however, it presents two oreven three specialized regions, namelyand in order, ileum, colon and rectum(Fig. 145). The hind intestine variesgreatly in length and is frequently solong- as to be thrown into convolutions(Fig. 150). The ileum is short andstout in grasshoppers (Fig. 145); long,slender and convoluted in many carniv-orous beetles; and quite short in cater-pillars and most other larvae; its func-tion is absorption. The colon, oftenabsent, is evident in Orthoptera andLepidoptera and may bear {Benac
Entomology : with special reference to its biological and economic aspects . 44).Usually, however, it presents two oreven three specialized regions, namelyand in order, ileum, colon and rectum(Fig. 145). The hind intestine variesgreatly in length and is frequently solong- as to be thrown into convolutions(Fig. 150). The ileum is short andstout in grasshoppers (Fig. 145); long,slender and convoluted in many carniv-orous beetles; and quite short in cater-pillars and most other larvae; its func-tion is absorption. The colon, oftenabsent, is evident in Orthoptera andLepidoptera and may bear {Benacus,Dytiscus, Silphidae, Lepidoptera) a con-spicuous CcTcal appendage (Figs. 148, 150) of doubtful func-tion, though possibly a reservoir for excretions. The coloncontains indigestible matter and the waste products of diges-tion, including the excretions of the Malpighian tubes. Therectum (Fig. 145) is thick-walled, strongly muscular and oftenfolded internally. Its office is to expel excrementitious matter,consisting largely of the indigestible substances chitin, cellulose. Digestive system of Belos-toma. c, csecum; i, ileum;m, mid intestine; mt, Mal-pighian tubes; r, salivaryreservoir; s, salivary gland.•—After LocY, from theAmerican Naturalist. ANATOMY AND PHYSIOLOGY 121 and chlorophyll. The rectum terminates in the anus, whichopens through the last segment of the abdomen, always abovethe genital aperture. Histology.—The epithelial wall of the alimentary tract isa single layer of cells (Fig. 151), Avhich secretes the iiitima,or lining layer, and the basement nienihrane—a delicate, struc-tureless enveloping intima, which is contin-uous with the external cutic-ula, is chitinous in the foreand hind gut (which areectodermal in origin), butnot in the mid gut (entoder-mal), and usually exhibitsextremely fine transversestri?e, which are due prob-ably to minute pore the basementmembrane is a series of eir-cular muscles and outsidethese is a layer o
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectentomology, bookyear1
