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, Culex sp. lep., 

 Labrum-epipharynx; md., man- 

 dible; mx.L, maxillary lobe; 

 mx.p., maxillary palpus; hyp., 

 hypopharynx; li., labium; gl., 

 glossa; pg., paraglossa. 



