“The hypopharynx, a continuation of the lower edge (lamina) of the pharynx, most generally free, more or less produced, acute anteriorly, forms with the labrum the tube of the pump (antliæ). (The hypopharynx when obsolete, or coalesced with the canal of the proboscis, is the theca; in such a case the siphon or tube is formed by the theca and labrum.) Meanwhile the hypopharynx, the largest of all the trophi (omnium trophorum maximus), constitutes the chief piercing organ (telum) of Diptera. The hypopharynx is moved by protractor, most generally quite or very powerful, and by retractor muscles.
“The efferent duct of the thoracic salivary glands (ductus salivalis) perforates the hypopharynx, more or less near the base, that the saliva may be ejected through the canal into the wound, or that it may be conducted along the labella. Very rarely the salivary duct, perforating the hypopharynx, is continued in the shape of a free, very slender tube.
“The salivary duct behind the base of the hypopharynx forms the receptacle or receptaculum, provided with retractor and levator muscles.”
Fig. 83.—Labrum-epipharynx (lbr and eph) and hypopharynx (hyp) of Tabanus brominus: oe, posterior cylindrical portion of the œsophagus; a, anterior swollen portion of the same; ph, pharynx; ph.m, pharyngeal muscle; p.ph, protractor muscle of the pharynx; r.oe, retractor muscle of the œsophagus; r.ph, retractor muscle of the pharynx; f.oe, flexor muscle of the pharynx; t.oe, twisting muscle of the œsophagus; s.r, receptacle of the salivary duct; l, its elevator muscle; s, its retractor muscle; cl, clypeus.—After Meinert.
Fig. 84.—Œsophagus (oe), pharynx (ph) with epipharynx and labrum (lbr) of Asilus atricapillus: m, ph, pharyngeal muscle; sr, salivary receptacle; t, twisting; r, l′r, retractor muscles; other lettering as in Fig. 83.—After Meinert.
It has been carefully studied by Meinert in a species of Culex (Fig. 81), Simulium (Fig. 82), Tabanus (Fig. 83), and in Asilus (Fig. 84), where it is seen to attain enormous proportions. In the Hymenoptera, this organ in its most specialized condition is a trough-like rod, adapted for lapping nectar (Fig. 85, 86, hyp). The tongue or hypopharynx of the honey-bee has been elaborately described by Cheshire in his Bees and Bee Keeping.[[18]] He calls it the tongue or ligula. It is situated in a tube formed by the maxillæ and labial palpi, and can be partially retracted into the mentum. He states that it can move up and down in the tube thus formed, and then describes it as covered by a hairy sheath, its great elasticity being due to a rod running through its centre enabling it to be used as a lapping tongue. The sheath
“passes round the tongue to the back, where its edges do not meet, but are continuous with a very thin plaited membrane (G, pm) covered with minute hairs. This membrane, after passing towards the sides of the tongue, returns to the angle of the nucleus, or rod, over the under surface of which it is probably continued. The rod passes through the tongue from end to end, gradually tapering towards its extremity, and is best studied in the queen, where I trace many nerve threads and cells. It is undoubtedly endowed with voluntary movement, and must be partly muscular, although I have failed completely in getting any evidence of striation. The rod on the underside has a gutter, or trough-like hollow (cd, the central duct) which is formed into a pseudotube (false tube) by intercrossing of black hairs. It will also be seen that, by the posterior meeting of the sheath, the space between the folded membrane (G, sd) becomes two pseudotubes of larger size, which I shall call the side ducts.
