60 PARTIAL ORISMOLOGY. 



superficies of this membranaceous sheath, and generally at the angle of 

 the knee,, is found the mouth, covered by a small horny flap, and sur- 

 rounded by several bristly or lanceolate organs. Frequently, indeed, 

 this muscular sheath consists merely of a corneous channel, in which 

 the bristles lie (for example, Culex) ; and when thus formed, Fabricius 

 calls it haustellum; but the muscular sheath itself, proboscis styled 

 by Kirby and Spence the theca. 



The following, however, is the definition of these parts : The 

 SHEATH (PI. V. f. 1. A), whether it be muscular or horny, represents 

 the under lip, and is thence called labium, and the upper portion of 

 the knee the STALK (stipes); when horny posteriorly, it is the CHIN 

 Amentum'). The anterior terminal flap is merely a feeler, and 

 represents the labial palpi, which also only serve to supply the place 

 of a muscular lip ; it is called the KNOB (capitulum, PI. V. f. 1, A). 

 Upon the stalk, close to where the bristles, or setae of the mouth are 

 found, are placed the, from one to four-jointed, palpi (PI. V. f. 1 7- 

 c, c). The setae themselves are concealed by the superior, broader, 

 somewhat convex, upper lip (PI. V. f. 2 a, 3 a, and fig. 5, SHEATH, 

 vagina, Fab., valvula, Kirby and Spence) ; beneath it lie from one to 

 five setae, the two upper ones of which represent the MANDIBLES (the 

 same, b. b. the KNIVES, cultelli, of Kirby and Spence) ; the two lower 

 ones, the MAXILL/E (the same, c, c, the LANCETS, scalpella, of Kirby 

 and Spence); the middle one, the TONGUE (the same d, here called 

 glossarium) ; between them lies the MOUTH (the same, fig. 5, e). 

 When there is but one seta, it is the tongue : it is also the true 

 piercing instrument, which is pushed down into the upper channel of 

 the under lip ; and thus embraced by the terminal flaps, pierces into 

 the aliment ; the jaws move up and down by its side, and form, while 

 the suctorial ventricle distends, a decided pump, in explanation of 

 which we shall go into greater detail further on. 



The PROMUSCIS (rostrum, promuscis of Kirby and Spence, PI. V. 

 f. 8) is peculiar to the Hemiptera. It is much more uniform in its 

 construction than the proboscis, although it generally consists of the 

 same identical parts. We must distinguish in it the small triangular 

 plano-convex UPPER LIP, (labrum, fig. 8, 9, and 11, a, from above, 

 fig. 14 from beneath), which incases the commencement of the pro- 

 muscis from above, and is attached to the clypeus ; and the, from three 

 to five-jointed, sheath (fig. 8. b), which consists of two equal lateral 

 flaps, which may represent the maxillae and their palpi, and four fine 

 setae (fig. 10, c, c, and d, d), which, as in the flies, are analogous to 



