The Collaborative International Dictionary
Submentum
Submentum \Sub*men"tum\, n.; pl. Submenta. [NL. See Sub-, and Mentum.] (Zo["o]l.) The basal part of the labium of insects. It bears the mentum.
Wiktionary
submentum
n. (context zoology English) The basal part of the labium of insects, which bears the mentum.