Half hours with insects . toughness tothe tube. There is a third loose investingmembrane, the so-called peritoneal trachea originates from a spiracle orbreathing hole, of which there are usuallynine on each side of the body. These spiracles, or stigmata(Fig. 101, act), open by a slit into an inner chamber (eh),guarded by a muscle (m). The air thus admitted is carriedinto every part of the body by the numerous fig. subdivisions of these tubes, which forma beautiful net-work of silvery threads whenfilled with air. They are bathed by the bloodwhich is everywhere oxygenated by the
Half hours with insects . toughness tothe tube. There is a third loose investingmembrane, the so-called peritoneal trachea originates from a spiracle orbreathing hole, of which there are usuallynine on each side of the body. These spiracles, or stigmata(Fig. 101, act), open by a slit into an inner chamber (eh),guarded by a muscle (m). The air thus admitted is carriedinto every part of the body by the numerous fig. subdivisions of these tubes, which forma beautiful net-work of silvery threads whenfilled with air. They are bathed by the bloodwhich is everywhere oxygenated by the airin these fine tubes. Numerous beetles and water bugs haveno special apparatus for breathing in thewater. The Dytiscus when it wishes tobreathe rises to the surface, tail foremost,bends the end of its abdomen so as to allow the air to passinto the spiracles under the eljtra, and scuttles down to thebottom in great apparent haste, with a bubble of air attachedto the tip of the body. When its supply of air is exhausted 10. Spiracle. Packakd] insects of THE POND AND STREAM. 139 it is forced to rise for more. In tlie travels of Colymbetes,a near all} of Dytiscus, around the jar in which we havewatched its movements, it often makes a squeaking sound,which we have heard at night as often as by day. This noisecan be readily produced artificially by rubbing the end ofthe abdomen against the elytra, or wing covers. In thisbeetle there are six pairs of abdominal spiracles, but thebasal pair are nearly three times as large as the others, andinto these most of the air probably enters. In handling thisbeetle one is apt to be pricked by the sternal spine, whichextends back of the insertion of the hind legs and is assharp as a needle. How useful it may be to the insect inpusliing its way through any obstacle may be demonstratedb} holding it tightly between the fingers ; here even it man-ages to push its way out and drop to the ground. All thewater beetles fly about in the night, exchanging
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectinsects, bookyear1881
