Labellum (insect anatomy)

In entomology, the term labellum has been applied variously and in partly contradictory ways.

One usage is in referring to a elongation of the labrum that covers the base of the rostrum in certain Coleoptera and Hemiptera.

[1] In contrast, the most common current use of the term is in the anatomy of the mouthparts of Diptera, particularly those in which the labium forms the bulk of the proboscis, such as in the housefly family.

Typically, the labium is expanded distally into a pair of fleshy labella.

In the early twentieth century it was argued that the labella are the modified labial palps, and that point of view still is seen as having merit.