Fig. 71.—Section through the anterior part of the head of Anabrus (the mandibles removed), showing the relations of the hypopharynx (hyp) to the opening of the salivary duct (sd): g, galea; l, lacinia; mt, mentum; oe, œsophagus; lbr, labrum; cl, clypeus.
In the Locustidæ (Anabrus, Fig. 71) the tongue (hypopharynx) is a broad, somewhat flattened lobe arising from the upper part of the base of the mentum and behind the palpifer. This lobe is cavernous underneath, the hollow being the salivary receptacle (sr); the latter is situated over the opening of the salivary duct, which is placed between the base of both the hypopharynx and the labium. The salivary fluid apparently has to pass up and around on each side of the hypopharynx in order to mix with the food.
These relations in the Orthoptera are also the same in the Perlidæ, where the hypopharynx is well developed, forming an unusually large tongue-like mass, nearly filling the buccal cavity.
Fig. 72.—Lingua of a May-fly, Heptagenia longicauda, ×16: m, central; l, lateral pieces.—After Vayssière from Sharp.
In the Odonata the lingua is a small, rounded lobe, as also in the Ephemeridæ; in the nymph, however, of Heptagenia (Fig. 72) it is highly developed, according to Vayssière, who seems inclined to regard it as representing a pair of appendages. The tongue in Hemiptera is said by Léon to be present in Benacus griseus (Say) and to correspond to the subgalea of Brullé or hypodactyle of Audouin (Fig. 73), but this appears to correspond to the labium proper, rather than a true lingua, the latter not being differentiated in this order. In the Coleoptera the lingua is rather small. In beetles, as Anopthalmus (Fig. 74), it forms a setose lobe; and a well-developed nerve, the lingual nerve, passes to it, dividing at the end into several branches (n-l). In Sialis the lingua is short, much less developed than usual, being rounded, and bears on the edge what appear to be numerous taste-hairs, like those on the ends of the maxillary and labial palpi.
Fig. 73.—A, labium of Zaitha anura. B, of Z. margineguttata. C, of Gerris najas: mt, mentum; lp, labial palpi; sg, subgalea; l, lacinia (= intermaxillare and præmaxillare of Brullé); g, galea.—After Léon.
In the adult Panorpidæ the lingua is a minute, simple lobe.