Mentum: a labial sclerite bearing the movable parts; attached to and sometimes fused with the sub-mentum; corresponds to the (united) stipes of maxillae: in Coleoptera, what is usually called mentum is really submentum: in Diptera, the term is applied to the posterior oral margin: in Hymenoptera, is part of "tongue," the second joint bearing the labial palpi, paraglossae and ligula.
Merdivorous: feeding upon dung or excrement: see scatophagous.
Meriaeum: the posterior inflected part of the metasternum in Coleoptera.
Meroistic: ovaries that secrete yolk or vitellaginous cells as well as ova.
Mesad: extending or directed toward the median plane.
Mesal: pertaining to, situated on or in the median plane of the body.
Mesenchym: that portion of the mesoderm that produces the connective tissues of the body.
Mesenteron: the mid-gut, stomach or chylific ventricle: the middle portion of the primitive intestinal canal, lined with entoderm.
Mesepimeron: in Odonata: the sclerite between humeral and first lateral suture.
Mesepisterna: in Odonata,- the oblique lateral pieces of mesothorax, meeting dorsally in a ridge.