hypostome

hypostome also hypostoma (noun; Greek hypo, under; stoma, mouth): 1. (Arthropoda: Chelicerata) In Acari, forming the ventral-median wall of the gnathosoma; fused with the pedipalps in most groups, but in ticks a toothed structure between the pedipalps.

2. (Arthropoda: Crustacea) The metastoma.

3. (Arthropoda: Diplopoda) The gula.

4. (Arthropoda: Insecta) The anteroventral part of the head including between the antennae, eyes and mouth of Diptera; the ventral part of the head of Hemiptera.

5. (Arthropoda: Trilobita) The median preoral plate or labrum.