Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 532 INSECTA. Amongst the secretory glands of insects the ylruirhdw odoriferce, the wax-glands, spinning-glands and jioison (/lands are to be mentioned. Of these, the first, to which belong the anal glands which we have already mentioned (fig. 440), lie beneath the covering of the body and secrete, usually between the articulations, strongly smelling fluids. In the buys there is an unpaired piriform gland in the metathorax, which pours out its secretion by an opening between the hind legs
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0101clau Year: 1884 532 INSECTA. Amongst the secretory glands of insects the ylruirhdw odoriferce, the wax-glands, spinning-glands and jioison (/lands are to be mentioned. Of these, the first, to which belong the anal glands which we have already mentioned (fig. 440), lie beneath the covering of the body and secrete, usually between the articulations, strongly smelling fluids. In the buys there is an unpaired piriform gland in the metathorax, which pours out its secretion by an opening between the hind legs and gives rise to the notorious smell. Unicellular cutaneous glands have been shewn to exist in different parts of the body of insects, and, like the of vertebrates, seem to secrete an oily liquid, which serves to lubricate the joints. Similar glandular tubes of the integument, which may be called wax-glands, secrete white threads and flakes, which cover the body as with a kind of powder or wool (Plant lice, tig. 441). Spinning-glands occur exclusively in larvae and serve for the produc- tion of webs and cases. When these glands have the form of two or more less swollen and elongated tubes (sericter I a) opening behind the mouth, they may be com- pared to a special form of salivary gland, which they also resemble in their structure. The larva of the ant- lion has its spinning organs at the opposite end of the body; the wall of the rectum, which is shut off from the chylitic ventricle, taking the place of the sericteria. The poison glands, which are present in the female Hymenoptera\ consist of two simple or branched tubes, the common duct of which is dilated to form a vesicular reservoir for the secreted fluid, which consists of formic acid. The end of this reservoir is connected with the poison spine. Vascular system.—The blood, which is usually colourless but not a. FIG. 441.—The wax glands and the prominences on which they open of an Aphide (Sc
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