=The basal or gular region of the head.=—At the hinder part of the head is the opening (occipital foramen) into the trunk. The cheek (gena) is the side of the head, and to its inner wall is attached the mandibular muscle; it thus forms the region behind the eye and over the base of the mandibles. In the Termitidæ, where the head is broad and flat, it forms a distinct piece on the under side of the head bounding the gulo-mental region (Fig. 28). In the Neuroptera (Corydalus, Fig. 29, and Mantispa, Fig. 30) it is less definitely outlined.
FIG. 29.—Head of _Corydalus cornutus_, ♂: _A_, from above. _B_, from beneath. _C_, from the side. _a. cly_, clypeus anterior; _p. cly_, clypeus posterior; _lbr_, labrum; _md_, mandible; _mx_, base of first maxilla; _mp_, its palpus; _m_, mentum; _sm_, submentum; _plpr_, palpifer; _lig_, fused second maxillæ; _ant_, antenna; _occ_, occiput. ]
FIG. 28.—Head of _Termopsis angusticollis_, seen from beneath, showing the gena and gula: _m_, mentum; _sm_, submentum; _labr_, under side of the labrum; _x_, hypopharyngeal chitinous support. ]
All the gulo-mental region of the head appears to represent the base of the second maxillæ, and the question hence arises whether the submentum is not the homologue of the cardines of the first maxillæ fused, and the mentum that of the stipites of the latter also fused together. If this should prove to be the case, the homologies between the two pairs of maxillæ will be still closer than before supposed. Where the gula is differentiated, this represents the basal piece of the second maxillæ. In Figs. 28, 29, 30, and 31, these three pieces are clearly shown to belong to the second maxillary segment. It is evident that these pieces or sclerites belong to the second maxillary or labial segment of the head, as does the occiput, which may represent the tergo-pleural portion of the segment. Miall and Denny also regarded the submentum as the basal piece of the second maxillæ.
FIG. 30.—Head of _Mantispa brunnea_, under side: _e_, eye; other lettering as in Fig. 29. ]
FIG. 31.—Head of _Limnephilus pudicus_, under side: _e_, eye; _l_, ligula; _p_, palpifer; _lp_, labial palpi. ]
=The occiput= (Fig. 29, _B_, _C_), as stated beyond, is very rarely present as a separate piece; in the adult insect we have only observed it in Corydalus. The occipital region may be designated as that part of the head adjoining and containing the occipital foramen. Newport considers the occiput as that portion of the base of the head “which is articulated with the anterior margin of the prothorax. It is perforated by a large foramen, through which the organs of the head are connected with those of the trunk. It is very distinct in Hydroüs and most Coleoptera, and in some, the Staphylinidæ, Carabidæ, and Silphidæ is constricted and extended backwards so as to form a complete neck.” (See also p. 51.)