The mentum lies in the centre of the ventral headcapsule. In Tanypodinae the mentum is reduced to a ventromentum and, in some genera, a dorsomentum with teeth Mentum Tanypodinae. In Orthocladiinae and Chironominae the mentum is a very pronounced toothed plate (only absent in Potthastia gr. longimana) with a very high diagnostic value Mentum Orthocladiinae, Mentum Chironominae.

Alternative form for Mentum : mental.