ligula

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A strap-shaped or tonguelike structure, especially the terminal portion of the labium in the mouthparts of certain insects.

from The Century Dictionary.

• noun In botany, same as ligule.
• noun In entomology: A fleshy, membranaceous, or horny anterior part of the labium, attached to the inner surface of the mentum, by which it is sometimes entirely concealed; the terminal or distal one of the three component parts of the labium.
• noun A process on the elytra of certain beetles. See elytral.—
• noun In anatomy, a band of white nervous substance bordering the membranous covering of the posterior part of the fourth ventricle of the brain on each side, and extending from the clava to the striæ acusticæ, where it winds around the restiform bodies. Also called tænia ventriculi quarti, ala pontis, and ponticulus.
• noun [capitalized] A genus of simple cestoid worms, type of the family Ligulidæ, having an unsegmented elongated body with two lateral depressions at the head end, and numerous sets of sexual organs in longitudinal series opening on the median line of the body. These endoparasites inhabit fishes and amphibians, and acquire their matured character in water-birds.
• noun [capitalized] A genus of mollusks.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Bot.) See ligule.
• noun The central process, or front edge, of the labium of insects. It sometimes serves as a tongue or proboscis, as in bees.
• noun A tongue-shaped lobe of the parapodia of annelids. See Parapodium.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A strap or strap-shaped object, especially such a development in plants or insects