. Elementary textbook of economic zoology and entomology. Zoology; Insect pests. 146 ECONOMIC ZOOLOGY AND ENTOMOLOGY four piercing stylets are the greatly modified mandibles and maxillae, and the tubular sheath, which has a narrow longi- tudinal slit along its upper side, is the much modified labium. The labrum is reduced to a very small triangular piece at the base of the sheath, and the maxillary palpi are wanting. The labial palpi are also wanting, or are sometimes present as two small feelers rising from the base of the labial sheath. Insects with this type of mouth- parts have muscles run
. Elementary textbook of economic zoology and entomology. Zoology; Insect pests. 146 ECONOMIC ZOOLOGY AND ENTOMOLOGY four piercing stylets are the greatly modified mandibles and maxillae, and the tubular sheath, which has a narrow longi- tudinal slit along its upper side, is the much modified labium. The labrum is reduced to a very small triangular piece at the base of the sheath, and the maxillary palpi are wanting. The labial palpi are also wanting, or are sometimes present as two small feelers rising from the base of the labial sheath. Insects with this type of mouth- parts have muscles running from the top of the pharynx or throat cavity to the top of the head which, when contracted, expand the pharynx and make a pump- ing or sucking organ of it. Mouth-parts of Mosquito.— The piercing and sucking beak of the mosquito is made up in much the same way as that of the squash bug and cicada. That is, there is a tubular sheath, narrowly open from base to tip along the middle of its upper side, in which lie a number of sharp, slender stylets, which can project be- yond the edge of the sheath and pierce or lacerate plant tissue or the skin of animals. The sheath is the much modified under lip or labium, while the needles are the modified mandibles and maxillae and two additional ones called labrum-epipharynx and hypopharynx. That is, they are outgrowths from the upper and lower walls of the mouth or throat (pharynx). Thus the mosquito has six piercing needles held together in its beak, instead of four as with the cicada and squash-bug and their allies. Or rather this is true only of the female mosquito, for the male mosquito lacks two of the stylets, probably the mandibles, and never, or but rarely, pierces the skin of animals to suck blood. There is. FIG. 62.—Mouth-parts of a female mosquito, Cnlcx sp. Icp., Labrum-epipharynx; md., man- dible; , maxillary lobe; , maxillary palpus; hyp., hypopharynx; //., labium; gl., glossa; pg., Please note t
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