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In the Diptera the hypopharynx reaches its highest development as a large, stout, awl-like structure.

Meinert, in his detailed and elaborately illustrated work, Trophi Dipterorum (1881), has made an advance on our knowledge of the hypopharynx and its homologies, both by his evidently faithful descriptions and dissections, and by his admirably clear figures.

Fig. 81.—Culex pipiens, section of head: oe œsophagus; sm, upper muscle, lm, lower muscle of the œsophagus; ph, pharynx; rm, retractor muscle of the receptacle (r) of the salivary duct (s.d); lbr, labrum; ep, left style of the epipharynx; f, part of front of head.—After Meinert.

Fig. 82.—Pharynx and hypopharynx of Simulium fuscipes: lph, lower lamina of the pharynx; p, the salivary duct (s.d) perforating the pharynx; o, orifice of the duct; shp, styles of the hypopharynx; mph, membranous edge of the hypopharynx; m, protractor muscle of the pharynx; gp, gustatory papillæ.—After Meinert.

“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.