entomology Entomology () is the science, scientific study of insects, a branch of zoology. In the past the term "insect" was less specific, and historically the definition of entomology would also include the study of animals in other arthropod groups, such ...

, 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 Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

and

Hemiptera Hemiptera (; ) is an order (biology), order of insects, commonly called true bugs, comprising over 80,000 species within groups such as the cicadas, aphids, planthoppers, leafhoppers, Reduviidae, assassin bugs, Cimex, bed bugs, and shield bugs. ...

. In contrast, the most common current use of the term is in the anatomy of the mouthparts of

Diptera Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

, particularly those in which the labium forms the bulk of the proboscis, such as in the housefly family. Typically, the labium is expanded

distally Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

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.Crampton, G. C.; The sclerites of the head and the mouthparts of certain immature and adult insects. Ann. Ent. Soc. Am. 14, pp. 65-103. In flies such as the mosquitoes, that have long

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

e, the labella are two separate organs, attached to the proboscis only at their bases, but in the flies with short antennae, such as the house fly, they are more or less fused to form a single structure. Flies with fused labella have food channels in the surface of the labella. These are called ''pseudotracheae''. They form the "spongy" part of a housefly's "tongue".

References

Insect anatomy {{insect-anatomy-stub