FIG. 50.—Mandible of _Copris carolina_.—After Smith. _A_′_C. anaglypticus_. _A_ (figure to right), do. of _Leistotrophus cingulatus_; _B_, of _Phanæus carnifex_; _g′_, end of galea,—_g_, enlarged; _c_, conjunctivus. _C_, of _Meloë angusticollis_: _l_, lacinia; _a_, lacinia enlarged. ]
Mandibles are wanting in the adults of the more specialized Lepidoptera, being vestigial in the most generalized forms (certain Tineina and Crambus), but well developed in that very primitive moth, Eriocephala (Fig. 51). They are also completely atrophied in the adult Trichoptera, though very large and functional in the pupa of these insects (Fig. 52), as also in the pupa of Micropteryx (Fig. 53). They are also wanting in the imago of male Diptera and in the females of all flies except Culicidæ and Tabanidæ.
They are said by Dr. Horn to be absent in the adult _Platypsyllus castoris_, though well developed in the larva; and functional mandibles are lacking in the Hemiptera.
=The first maxillæ.=—These highly differentiated appendages are inserted on the sides of the head just behind the mandibles and the mouth, and are divided into three lobes, or divisions, which are supported upon two, and sometimes three basal pieces, _i.e._ the basal joint or _cardo_, the second joint or _stipes_, with the _palpifer_, the latter present in Termitidæ (Fig. 54, _plpgr_), but not always separately developed (Fig. 55). The cardo varies in shape, but is more or less triangular and is usually wedged in between the submentum and mandible. It is succeeded by the stipes, which usually forms the support for the three lobes of the maxilla, and is more or less square in shape.
FIG. 51.—Mandible of _Eriocephala calthella_: _a_, _a′_, inner and outer articulation; _s_, cavity of the joint (acetabulum); _A_, end seen from one side of the cutting edge.—After Walter. ]
FIG. 52.—_A_, Pupa of _Phryganea pilosa_.—After Pictet. _B_, mandibles of pupa of _Molanna angustata_.—After Sharp. ]
FIG. 53.—Pupa of _Micropteryx purpuriella_, front view: _md_, mandibles; _mx.p_, maxillary palpus, end drawn separately; _mx.’p_, labial palpi; _lb_, labrum; _A_, another view from a cast skin. ]
The three distal divisions of the maxilla are called, respectively, beginning with the innermost, the _lacinia_, _galea_, and _palpifer_, the latter being a lobe or segment bearing the _palpus_. The lacinia is more or less jaw-like and armed on the inner edge with either flexible or stiff bristles, spines, or teeth, which are very variable in shape and are of use as stiff brushes in pollen-eating beetles, etc. The galea is either single-jointed and helmet-shaped or subspatulate, as in most Orthoptera, or 2–jointed in Gryllotalpa, or lacinia-like in Myrmeleon (Fig. 55, _C_); or, in the Carabidæ (Fig. 56) and Cicindelidæ, it is 2–jointed and in form and function like a palpus.