The Collaborative International Dictionary of English v.0.48:

Dimera \Dim"e*ra\, n. pl. [NL., fr. Gr. di- = di`s- twice + ?
   part.] (Zool.)
   (a) A division of Coleoptera, having two joints to the tarsi.
   (b) A division of the Hemiptera, including the aphids.
       [1913 Webster]