In the adult Panorpidæ the lingua is a minute, simple lobe.
FIG. 74.—Section through head of a carabid, _Anopthalmus telkampfii_: _br_, brain; _f. g_, frontal ganglion; _soe_, subœsophageal ganglion; _co_, commissure; _n. l_, nerve sending branches to the lingua (_l_); _mn_, maxillary nerve; _mx_, 1st maxilla; _mm_, maxillary muscle; _mx′_, 2d maxilla; _mt_, muscle of mentum; _le_, elevator muscle of the œsophagus; _l_ of the clypeus, and a third beyond raising the labrum (_lbr_); _eph_, epipharynx; _g_, _g_, salivary glands above; _g_^2, lingual gland below the œsophagus (_oe_); _m_, mouth; _pv_, proventriculus; _md_, mandible. _A_, section passing through lingual gland (_g_^2). ]
In the larval Trichoptera the spinneret is well developed, and in structure substantially like that of caterpillars, and it is plainly the homologue of the hypopharynx, receiving as it does the end of the silk-duct.
In the adult Trichoptera the hypopharynx is a very large, tongue-like, fleshy outgrowth, and is, both in situation and structure, since it contains the opening of the silk-duct, exactly homologous with the hypopharynx of insects of other orders, being somewhat intermediate between the fleshy tongue or lingua of the mandibulate insects, especially the Neuroptera, and the hypopharynx of the bees (Fig. 86). Lucas describes and figures it under the name of “haustellum,” but does not homologize it with the hypopharynx. The caddis-flies have been observed to drink water and take in both fluid and fine particles of solid food, and to use the haustellum for this purpose, the end being provided with minute sense-organs like those on the first maxillary lacinia, and possibly of a gustatory nature.
FIG. 75.—Head of _Anabolia furcata_: _A_, front view, showing the labrum removed. _B_, side view; _ant_, antenna; _oc_, ocellus; _ol_, labrum; _gh_, articulatory process; _cmx__{ 1}, cardo; _stmx__{ 1}, stipes; _lemx__{ 1}, outer lobe (galea); _ptmx__{ 1}, palpus of 1st maxilla; _pl_, palpus of 2d maxilla; _ha_, haustellum; _so_, gustatory pits; _spr_, opening of salivary duct; _chsp_, chitinous hook of the clasp; _spr_, furrow or gutter of the haustellum.—After Lucas. ]
FIG. 76.—Hypopharynx of _Eriocephala calthella_: _lig_, ligula, its membranous hinder edge; _lig′_, anterior horny edge of the ligula-tube opening outwards; _hp_, contour of the hypopharynx; _mi_, mala interior (lacinia); _me_, mala exterior (galea), of second maxilla; _mx′ p_, labial palpus.—After Walter. ]