THE HEAD. 59 



TURGID {p. turgidi, PI. IV. f. 22), when the last joint has the 

 appearance of a distended bladder (G ryllotalpa). 



EXCAVATED ( p. excarati, PI. IV. f. 23), when the same joint is 

 concave at its extremity. (Compare below in the Anatomy of the 

 Organs of the Senses, 198). 



TRUNCATED (p. truncuti), when the last joint appears to terminate 

 abruptly (Prionus). 



DIVIDED (p.fasi), when the last joint is divided longitudinally. 



PILOSE (p. pilosi), when the joints are covered with sharp stiff 

 bristles (Cicindela, PI. IV. f. 10). 



SQUAMOSE (p. squamosi), covered with broad scales (Lepidoptera, 

 PI. IV. f. 24 and 25). 



ELONGATE (p. elongati), are those palpi Avhich stand freely from 

 the mouth (Carabus). 



SHORT (p. brevissimi), when, in looking at the mouth, they are not 

 perceived (Curculionodea, Libellulina). 



VERY LONG (p. longissimi) , when they are longer than the head, or 

 even than the antennas (Hydrophilus). 



UNEQUAL (p. intequales), when single joints take a different form 

 (Banchus, Ichneumon, PI. IV. f. 26). 



EQUAL (p. cequales}, on the contrary, when this is not the case. 



SUCTORIAL ORGANS OF THE MOUTH. 

 70. 



The suctorial organs (instrumenta suctoria) are, fundamentally, 

 merely the masticating ones transformed, or rather those stopped upon 

 a lower stage of development, for a precise investigation clearly redis- 

 covers the same identical organs. We however find no general uniformity 

 among them, excepting in their function that of taking nourishment 

 by suction ; for every order of insects with suctorial organs has a pecu- 

 liar and then throughout all the families which compose it, a very 

 uniform structure. 



We thence distinguish the following principal forms: the PRO- 

 BOSCIS (proboscis), or HAUSTELLUM (Jiaustellum), we find in the 

 Diptera only. It consists of a membranaceous or more or less fleshy 

 organ, which descends in a perpendicular direction from the orifice of 

 the mouth, and which in general shortly from its origin is geniculated 

 forward, and terminates in a napper-shaped suctorial surface. Upon the 



