A palp on the outer side,
A galea (hood),
A lacinia (blade), on the inner side.
The galea (hood) of the 3rd pair of jaws is sometimes called the paraglossa.
A tongue-like process may be developed from the front wall of the mouth (epipharynx), or from the back wall (hypopharynx or lingua).[49] Both epipharynx and hypopharynx project into the mouth, and, in some Diptera, far beyond it.
The tip of the labium is sometimes produced into a long tongue, called the ligula (strap).
The mouths of Insects may be classed as:—
Biting.—Orthoptera, Neuroptera, Coleoptera (in some Coleoptera a licking tongue is developed), most Hymenoptera.
Licking and Sucking.—Some Hymenoptera—e.g., Honey Bee.
Sucking.—(a) With lancets—Diptera, Hemiptera. (b) Without lancets—Lepidoptera.
The reference of these to a common plan, and the determination of the constituent parts, is mainly the work of Savigny. Mouth-parts were made the basis of the classification of Insects by Fabricius (1745–1808).