HEMIPTERA 355 



and ridges ; and between the maxillary setas are two canals, the upper 

 one (/c) for the passage in of food, the lower one {sc) for the passage 

 out of saliva. The tip of the mandibular setas are barbed (Fig. 405, 

 md) ; their function is that of piercing the tissue fed upon and holding 

 the setajin place; while the tips of the maxillary sette, which are acute 

 and fluted, probe the tissue, take up the fluid food, and eject the saliva. 



Within the head each seta is connected with a chitinous lever, or 

 with a series of two levers which in turn articulate with the head- 

 capsule; the in-and-out move- 

 ments of the setae are produced 

 by muscles extending from the 

 head-capsule to them and to 

 the levers connecting them 

 with the wall of the head. Fig- 

 ure 407 represents the articu- 

 lation of a mandibular seta of 

 a squash-bug, as represented 

 by Tower; and in the next 

 chapter the relations of both 

 the mandibular setas and the 



maxillary setag to the head- Fig. 407 .^Articulation of a mandibular 



capsule in a cicada are rep- seta with the wall of the head: wJ,man- 



, 1 /-p- z- \ dibular seta; a and OjChitmous levers;^, 



resented (rig. 405;. wall of the head; rm, retractor muscles; 



Correlated with the de- ^7w, protractor muscle. (From Tower.) 

 velopment of the hemipterous 



type of mouth-parts there is a remarkable specialization of the phar- 

 ynx, which fits it as a sucking organ, and the development of an 

 organ for forcing out the saliva, which is known as the salivary pimip. 

 A detailed account of these organs is given by Bugnion and Popoff 



Cii). 



Most of the Hemiptera protect themselves by the emission of a 

 disagreeable odor. In the adult stink-bugs (Pentatomidas) this is 

 caused by a fluid which is excreted through two openings, one on 

 each side of the ventral aspect of the thorax, behind or near the middle 

 coxa. These openings are termed the osteoles. Each of these is 

 usually in some kind of an open channel styled the osteolar canal, 

 and this is surrounded by a more or less rugged and granulated 

 space, the evaporating surface. In the nymphs the stink-glands 

 open on the dorsal aspect of the abdomen. In the bedbug (Cimex), 

 the stink -glands open in the dorsal wall of the first three abdominal 

 segments. The legs of the Hemiptera vary greatly in form, but the 

 tarsi are rarely more than three-jointed. The lateral margin of the 

 abdominal segments is much developed in several families, and forms 

 a flat, reflexed or vertical border to the abdomen, which is called the 

 connexivum. 



In the Hemiptera the metamorphosis is gradual; 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 



