mesothorax

from The Collaborative International Dictionary of English v.0.48

Mesothorax \Mes`o*tho"rax\, n. [Meso- + thorax: cf. F.
   m['e]sothorax.] (Zool.)
   The middle segment of the thorax in insects. See Illust. of
   {Coleoptera}.
   [1913 Webster]