Identifier: americanauniver08beac (find matches)
Title: The Americana : a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc. of the world
Year: 1903 (1900s)
Authors: Beach, Frederick Converse, 1848-1918 Rines, George Edwin, 1860-
Subjects: Encyclopedias and dictionaries
Publisher: New York : Scientific American Compiling Dept.
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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of insects is their mode of respira-tion. This is effected by an intricate system ofinternal air-tubes (tracheae), which are filledwith air by openings (spiracles) in the sides ofthe body; of these spiracles there are from oneto two pairs in the thorax, and eight pairs inthe abdomen. The tracheae are kept perma-nently open by a series of threads (taenidium)each of which makes from three to five turnsaround the thin tube; in this way the entiretracheal branch is provided with what at firstwas supposed to be a continuous spiral thread.The slit-like openings of the spiracles areguarded by a grate of stiff hairs to prevent theingress of dust, etc. It should be borne inmind that no insect breathes through its mouth,but through the spiracles. Hence the efficacyof all oily or greasy substances in destroyingevery kind of insect in whatever stage of growth;wherever the oil touches the body a thin filmspreads over it, covering the air-openings so thatthe insect soon dies by asphyxiation. Though
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INSECTS insects have a delicate pulsating tubular heart,they have DO arteries and veins, since the airin the trachea seeks the blood in the remotestparts ot the body. The blood is thin and color-less, l be aquatic larvae and a very few perfect insects breathe by external tracheal Rills, thespiracles being in such cases often absent. Thegenital opening is always situated near the endoi the body, in front of the vent on the underside. Besides a complicated digestive canal, in-sects have urinary tubes opening into the end ofthe intestine. The nervous system consists, besides thebrain, of a chain of ganglia the greatest numberof which is 13, but which become more or lessfused in the more specialized groups, especiallyin the flies. The brain is remarkably complex,in accordance with the varied and complicatedmovements of the segmented body and jointedappendages, all capable of different kinds ofmotions. Sense of Sight.— The compound or facettedeyes (ommatea) are composed of numeroussimple

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