122 STATES OF INSECTS. 



like the mandibles of other insects, but merely detach 

 particles of food by digging into it and tearing the fibres 

 asunder. In this operation they are probably assisted by 

 an acutely triangular dart-like instrument of a horny sub- 

 stance, which in some species (Musca vomitotia) is 

 placed between the two. In others this part is wanting. 

 Some Dipterous larvaa have two similar mandibles, but in- 

 stead of being parallel, they are placed one above the other; 

 ©tliers (Mmca domestica and meridiana) have but one such 

 mandible, and some have no perceptible mandible of any 

 kind. The mandibles of the larva of the crane-flies ( Tipula\ 

 which are transverse and unguiform, do not act against 

 each other, but against two other fixed, internally coiir 

 cave and externally convex, and dentated pieces a . 



Under-jaws (Maxilla). These are a pair of organs, 

 usually of a softer consistence, placed immediately under 

 the upper-jaws; but as they are usually so formed and si- 

 tuated as not to have any action upon each other, it is 

 probable that in general they rather assist in submitting 

 the food to the action of the mandibular, than in the com- 

 minution of it. In Lepidopterous larvae they appear to 

 be conical or cylindrical (at least in that of the cossus 

 so admirably figured by Lyonnet b ), and to consist of two 

 joints; which may, I imagine, be analogous to the upper 

 and lower portions of which the maxillae of perfect insects 

 usually consist. The last of these joints is surmounted 

 by two smaller jointed palpiform organs. If any part of 

 the maxillae can act upon each other, it is these organs 

 or palpi ; but it is evident they are not calculated for mas- 

 tication, although they may assist in the retention of the 



- 1 Reaum. v. 9. i.lf. 4. c c. IL h Traite Anatom. i. W.f. 1. h h. 



