Maxilla

Definition

One of a pair of segmented, usually posterior mouthparts in insects and other arthropods, located immediately behind the mandibles. Each maxilla typically comprises a basal cardo and stipes, bearing endite lobes (the lacinia and galea) that grasp and manipulate food, plus a multi-segmented palp that serves a gustatory and tactile sensory function. In chewing insects the maxillae work in concert with the mandibles to position and steady food; in fluid-feeding lineages they may be modified into stylets or other probe components.

Etymology

Latin diminutive of mala, jaw or cheekbone

Example

In a grasshopper, the toothed lacinia of each maxilla helps anchor plant material while the mandibles slice through it; the palps taste and explore the substrate before feeding begins.

Related Terms

• Mandible
• Labium
• Labrum
• hypopharynx
• cardo
• stipes
• lacinia
• Galea
• maxillary palp
• mouthparts

Usage Notes

The term applies broadly across arthropod groups but details vary: crustacean maxillae are often highly modified for filter-feeding, while in arachnids the homologous structures are subchelate and used in prey handling. Not to be confused with the vertebrate upper jaw bone (also called maxilla), which is unrelated in structure and embryonic origin. The adjectival form is maxillary.