Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget .. . xa-mined, and from whose drawings of the dissected parts theannexed figures (163) have been engraved. The sting of thebee, A, is formed of two portions placed laterally together, butcapable of being separated. The point, p, is directed a little upwards, and is a little curved :the barbs, seen still more highlymagnified at q, are about six innumber, and are placed on theunder surface, and their pointsdirected backwards. At thebase of the sting, e, there isa semicircular dilatation appa-rentl
Animal and vegetable physiology, considered with reference to natural theology, by Peter Mark Roget .. . xa-mined, and from whose drawings of the dissected parts theannexed figures (163) have been engraved. The sting of thebee, A, is formed of two portions placed laterally together, butcapable of being separated. The point, p, is directed a little upwards, and is a little curved :the barbs, seen still more highlymagnified at q, are about six innumber, and are placed on theunder surface, and their pointsdirected backwards. At thebase of the sting, e, there isa semicircular dilatation appa-rently intended to prevent theinstrument from being thrusttoo far out of the sheath (seenseparately at v), in which itmoves: it has also a long ten-don to which the muscles areattached. It is between theseplates, when approximated, thatthe poison flows from the orificeof the somewhat dilated extre-mity of the poison duct, d,which comes from the anteriorpart of the poison bag, b. Thisbag is of an oval shape, andis not the organ which secretesthe poison, but merely a receptacle for containing it: for it is. a FLIGHT OF INSECTS. 353 Although the greater number of insects havefour wings, there are many, such as the commonhouse fly, and the gnat, which have only compose the order Diptera (Fig. 162).In these insects we meet with two organs, con-sisting of cylindrical filaments, terminated in aclubbed extremity; one arising from each sideof the thorax (as seen in the above figure), inthe situation in which the second pair of wingsoriginate in those insects that have four are named the halteres, or poisers, fromtheir supposed use in balancing the body, oradjusting with exactness the centre of gravitywhen the insect is flying. Whatever may betheir real utility, they may still be regarded asrudiments of a second pair of wings; and theyafford, therefore, when thus viewed, a striking-instance of the operation of the tendency which conveyed into this bladder by means of a lo
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