122 STATES OF INSECTS. (Larva.) 
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 vomitoria) is placed 
between the two. In others this part is wanting. Some 
Dipterous larvee have two similar mandibles, but instead 
of being parallel, they are placed one above the other ; 
others (Musca domestica and Mesembrina meridiana) have 
but one such mandible, and some have no perceptible 
mandible of any kind. The mandibles of the larva of 
the crane-flies (Z¢pula), which are transverse and ungui- 
form, do not act against each other, but against two other 
fixed, internally concave and externally convex, and 
dentated pieces *. 
Under-jaws (Maxitim). 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 mandibulee, than in the com- 
minution of it. In Lepidopterous larvee they appear to 
be conical or cylindrical (at least in that of the cossus 
so admirably figured by. Lyonnet°), and to consist of two 
joints; which may, I imagine, be analogous to the upper 
and lower portions of which the maxillze of perfect insects 
usually consist. The last of these joints is surmounted 
by two smaller jointed palpiform organs. If any part of 
the maxillze 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 
@Reaum.v.9.4.1.f.4.cc.d1  ° Traité Anatom. t. i.f. 1. HH. 
