The Collaborative International Dictionary
Labellum \La*bel"lum\ (l[.a]*b[e^]l"l[u^]m), n.; pl. L. Labella (l[.a]*b[e^]l"l[.a]), E. Labellums (l[.a]*b[e^]l"l[u^]mz). [L., dim. of labrum lip.]
(Bot.) The lower or apparently anterior petal of an orchidaceous flower, often of a very curious shape.
(Zo["o]l.) A small appendage beneath the upper lip or labrum of certain insects.
Wiktionary
n. The lower central petal of orchid flowers, usually developed to be showy and attract pollinators.
Wikipedia
In botany, the labellum (or lip) is the part of the flower of an orchid or Canna, or other less-known genera that serves to attract insects, which pollinate the flower, and acts as a landing platform for them.
Labellum (plural: labella) is the Latin diminutive of labium, meaning lip.
The labellum is a modified petal and can be distinguished from the other petals and from the sepals by its large size and its often irregular shape. It is not unusual for the other two petals of an orchid flower to look like the sepals, so that the labellum stands out as distinct.
In orchids, the labellum is the modified median petal that sits opposite from the fertile anther and usually highly modified from the other perianth segments. It is often united with the column and can be hinged or movable, facilitating pollination. Often, the orchid labellum is divided into three or more lobes. Some have modified fleshy lumps on the upper surface generally referred to as the callus, with some being divided into multiple ridges or a central keel. When the callus is flat and broad, it is sometimes called a plate, which can have fringed margins. The callus can be highly modified with striking colors that may aid in pollinator deceit and mimicry.
The labellum in orchids is often large and complex enough that terminology describing relative positions for structures on it becomes useful: the hypochile is the basal portion nearer the connection with the rest of the flower, the mesochile is the middle portion, and the epichile is the distal portion.
Labellum (plural: labella) is the Latin diminutive of labium, meaning lip. These are anatomical terms used descriptively in biology:
- Labellum (botany), a part of a flower
- Labellum (insect anatomy), a part of the mouth of an insect
In entomology, the term labellum has been applied variously and in partly contradictory ways. One usage is in referring to a prolongation of the labrum that covers the base of the rostrum in certain Coleoptera and Hemiptera.
In contrast, the commonest 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. In flies such as the mosquitoes, that have long antennae, 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".
Usage examples of "labellum".
The gynostemium, whilst spontaneously moving, comes into contact with the viscid labellum, to which it adheres, until freed by the increasing tension of the parts or by being touched.
When the bee begins to gnaw the labellum, he unavoidably touches a tapering projection, which, when touched, transmits a vibration which ruptures a membrane, which sets free a spring by which a mass of pollen is shot, with unerring aim, over the back of the bee, who then departs on his errand of fertilization.
The gynostemium, whilst spontaneously moving, comes into contact with the viscid labellum, to which it adheres, until freed by the increasing tension of the parts or by being touched.