2. (Arthropoda: Insecta) The front of a verticle head between the compound eye above the mouth to vertex. a. In Hymenoptera between antennae and clypeus. b. In Diptera, below the frontal suture, often having grooves or fovea below the antennae; the mesofacial plate. c. In Ephemeroptera, the fused front and vertex
See also: facies.