4-62 EXTERNAL ANATOMY OF INSECTS. 



underneath with a double row of stout teetli ; and the 

 terminal one is more solid and harder, in the form of a 

 very sharp crooked claw, which in inaction is folded on 

 the first joint between the teeth. Under its extremity on 

 the outside is a minute orifice, destined to transmit a ve- 

 nomous fluid, which is conducted there by an internal 

 canal from the base of the first joint, where is the poison- 

 bag a . In the scorpion and harvest-man (Phalangium) 

 the mandible consists of two joints terminated by a chela 

 or double claw, the exterior one being moveable 5 . — ■ 

 M. Latreille, as has been before observed, regards these 

 not as representatives of the mandibles of hexapods, but 

 as replacing the interior pair of antennas, in the situation 

 of which they are precisely placed, of the Crustacea c : 

 and M. Savigny is of opinion that the Arachnida may in 

 some sort be defined as Crustacea without a head, and 

 with twelve legs, of which the two first pair are converted 

 into mandibles and maxilla?'*-. From the situation of the 

 organs in question, the first of these opinions seems pre- 

 ferable ; but the conversion of the legs in other cases, at 

 least the coxae, into organs of manducation, gives some 

 weight to the last. With regard to their use, it is said 

 to be to retain the insect which the animal has seized, 

 and to facilitate the compression which the maxillae exer- 

 cise upon it for the extraction of the nutritive matter e . 

 If this be correct, in this respect the mandibles may be 

 said to represent the maxillae of the mandibulate hexa- 

 pods ; and, vice versa, the sciatic maxillae, as they have 



a N. Diet. d'Hist. Nat. ii. 275—. Plate VII. Fig. 10. c'. 

 b De Geer t. xl./. 4. t. x.f. 7, 8. c See above, p. 18, 30 



d Savigny Anim. sans Vertebr. I. i. 62. 

 e N. Diet. d'Hist. Nat. ii. 277. 



