. Elements of zoölogy : a textbook. Zoology. 290 ARTICULATA : INSECTA. altogether forming a net-work of veins and veinlets. The five main veins, beginning at the front edge, are the costal, the sub-costal, the median, the sub-median and internal. Sometimes the median divides into two. The front or costal vein is undivided ; the sub-costal and median are divided into several branches ; the sub-median and inter- nal are generally simple. The piercer mentioned above is properly an ovipositor, and is in some cases a jointed tube, and is used for con- ducting eggs into holes where they are to be le
. Elements of zoölogy : a textbook. Zoology. 290 ARTICULATA : INSECTA. altogether forming a net-work of veins and veinlets. The five main veins, beginning at the front edge, are the costal, the sub-costal, the median, the sub-median and internal. Sometimes the median divides into two. The front or costal vein is undivided ; the sub-costal and median are divided into several branches ; the sub-median and inter- nal are generally simple. The piercer mentioned above is properly an ovipositor, and is in some cases a jointed tube, and is used for con- ducting eggs into holes where they are to be left to be hatched ; in other cases it is a scabbard containing a cen- tral borer, or saws in some cases, which are used in making holes in which eggs are to be deposited. The sting with which many insects, as bees and wasps, are provided is merely a modified ovipositor, and consists of a sheath cov- ering a sharp instrument for inflicting wounds, and con- necting with it inside of the body is a sac of poison. The digestive system of insects is quite complicated. It consists of a mouth variously modified in the different groups, a pharynx, a gullet, a first stomach or crop, a sec- ond stomach or gizzard, a small intestine, etc. In some kinds the mouth parts are modified for biting and chew- ing purposes; in others they are so modified as to be adapted for sucking organs. The parts called mandibles. Mandibles of different Insects. A, Beetle ; B. Grasshopper ; C> Dragon-fly ; D' Wasp ; E- Bedbug, (in which mandibles, maxilla, and labium are united to form the beak or jointed sucker) ; F- Musquito (with bristle-like mandibles) ; C- Cock-chafer. are situated on each side of the mouth opening, and they vary greatly in form and size. They usually consist of. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Tenney
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