Glossa

Definition

The central, often tongue-like lobe of the labium in insects, typically the primary gustatory and fluid-feeding structure. In bees and many nectar-feeding insects, the glossa is elongated, flexible, and often hairy or grooved to draw up liquids by capillary action; in some groups it is short and fused with the paraglossae. The glossa works with the galeae and laciniae to form a functional proboscis in fluid-feeding species.

Etymology

From Greek glossa (γλῶσσα), meaning 'tongue' or 'language'.

Example

In worker honey bees (Apis mellifera), the hairy glossa extends far beyond the other mouthparts and is rhythmically dipped into nectar pools; retraction brings the fluid into the food canal formed by the surrounding galeae.

Synonyms

• tongue (informal)
• ligula (when referring to the glossa plus paraglossae in some contexts)

Related Terms

• Labium
• paraglossa
• ligula
• Galea
• Proboscis
• hypopharynx
• nectarivory

Usage Notes

The term is sometimes used loosely for any tongue-like mouthpart, but strictly refers to the median lobe of the labium. Distinguish from hypopharynx (an internal tongue-like structure in the preoral cavity). In some taxonomic literature, 'ligula' refers to the entire terminal labial structure including glossa and paraglossae, while 'glossa' is reserved for the central lobe alone. The plural 'glossae' is standard in morphological descriptions.