A Text-book of Entomology / Including the Anatomy, Physiology, Embryology and Metamorphoses of Insects for Use in Agricultural and Technical Schools and Colleges as Well as by the Working Entomologist

by A. S. Packard

Fig. 66.—Second maxillæ of Pteronarcys californica.

Fig. 67.—Second maxillæ of Myrmeleon diversum.

Fig. 68.—Second maxillæ of Mantispa brunnea.

The hypopharynx.—While in its most generalized condition, as in Synaptera, Dermaptera, Orthoptera, and Neuroptera, this anterior median fold or outgrowth of the labium forming the floor of the mouth may retain the designation of “tongue,” lingua, or ligula; in its more specialized form, particularly when used as a piercing or lapping organ, the use of the name hypopharynx seems most desirable. And this is especially the case since, like the epipharynx, it is morphologically a median structure, and while the epipharynx forms the soft, sensitive roof of the mouth, or pharynx; its opposite, the hypopharynx, rises as a fold from the floor of the mouth, forming in its most generalized condition a specialized fold of the buccal integument. In certain cases, as in the honey-bee, the very long slender “tongue” or hypopharynx is evidently, as in the case of the epipharynx, a highly sensitive armature of the mouth.

In all insects this organ—whether forming a soft, tongue-like, anterior portion or fold of the labium, and “continuous with the lower wall of the pharynx,” or a hard, piercing, awl-like appendage (fleas and flies), or a long, slender, hairy or setose, trough-like structure like the “tongue” of the honey-bee—has a definite location at the end and on the upper side of the labium, and serves to receive at its base the external opening of the salivary duct.

The hypopharynx, as well shown in its lingua condition in Orthoptera, is continuous with and forms the anterior part or fold of the base of the coalesced second maxillæ. It does not seem to be paired, or to represent a pair of appendages.

Opinion regarding the homology of this unpaired piercing organ is by no means settled, and while there is a general agreement as to the nature of the paired mouth-parts, recent observers differ very much as to the morphology of the organ in question.

It is the langue or lingua of Savigny (1816), the ligula of Kirby and Spence (1828), the langue ou languette (lancette médiane du suçoir) of Dugès (1832), the lingua of Westwood (Class, ins., ii, p. 489, 1840), “the unpaired median piercing organ” (“the analogon of the epipharynx of Diptera”) of Karsten (1864), the “tongue” of Taschenberg (1880).