HEMIPTERA 



95 



triangular portion of the terminal part of the corium is separated as a dis- 

 tinct piece; this is the cuneus (Fig. 148, cu). 



The mouth-parts are formed for piercing and sucking. Without 

 dissection, they usually appear as a slender segmented beak arising from 

 the front part of the head (Fig. 149). The beak consists of the labium 



Fig. 147. — Diagram of a front wing of an antho- 

 corid: e, embolium. 



Diagram of a front wing of a mirid: 



Fig. i4g. — Head of Lethocerus: c, clypeus; /, la- 

 brum; Ip, labial palpi; y, y, maxillary sclerites. 



with possibly vestiges of the labial palpi combined with it. The beak is 

 deeply grooved on the dorsal surface forming a channel in which are four 

 long, slender setae or bristles, two of which are the much 

 modified mandibles and two the greatly changed maxilla?. 

 The beak is not a piercing organ; its function is to protect 

 and direct the seta? and to determine, by means of tactile 

 hairs at its tip, the place where the puncture should be made 

 by the setae (Fig. 150). 



The mandibular and maxillary setae when in use, are 

 pushed beyond the tip of the beak in order to pierce the 

 tissues of the plant on which the insect is feeding. 



Most of the Hemiptera protect themselves by the emis- 

 sion of a fluid having a disagreeable odor. In the stink- 

 bugs, PentatomidcB, the fluid is excreted through two 

 openings on the ventral side of the thorax near the middle 

 coxae. In the bedbugs the openings are in the dorsal wall of FlG lso _ Mouth . 

 the first three abdominal segments. p arts of Bu e- ( After 



In the Hemiptera the metamorphosis is incomplete ; the 

 newly-hatched young resembles the adult in the form of its body but lacks 

 wings. After one or two molts the wing-buds appear and become 

 larger and larger at successive molts. With the last molt there takes 

 place a great expansion of the wings, the change at this time being much 

 greater than at either of the previous molts. There are many wingless 

 forms in this order. In some species all individuals are wingless; in 

 others there are two forms of adults, the winged and the wingless. 



