—— Notes on the epipharynx and the epipharyngeal organs of taste in mandibulate insects. (Psyche, v, pp. 193–199, 222–228, 1889.)
Attachment of the head to the trunk.—The head is either firmly supported by the broad prothoracic segment in Orthoptera, many beetles, etc., into which it is more or less retracted, or it is free and attached by a slender neck, easily turning on the trunk, as in dragon-flies, flies, etc. In some insects there are several chitinous plates, situated on an island in the membrane on the under side of the neck; these are the “cervical sclerites” of Sharp, occurring “in Hymenoptera, in many Coleoptera, and in Blattidæ.”
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.