The mouthparts and upper food canal of the biting midge, Culicoides sanguisuga, are described with light, scanning electron, and transmission electron microscopy. The stylets (labrum, hypopharynx, mandibles, laciniae) are individually described so that their union into the piercingsucking syntrophium can be understoo. Labial anatomy and relationships to the syntrophium are also described. Syntrophial integrity is based on a complex system in which (1) the mandibles articulate with each other and with the hypopharynx; (2) the edges of the labrum are hooked over the sides of the mandibles; (3) the laciniae "clasp" the hypopharyngeal-mandibular complex to the labrum; and (4) the labellum holds the stylets together terminally. We propose that all muscles attached to the mandibles of the biting midge serve as retractors. This, combined with the fact that the mandibles have only one toothed edge (rearward-directed teeth on the lateral edge), suggests that retraction is the only active cutting stroke during biting. The mechanism contrasts with that of black flies (simuliids), which have mandibular protractors and retractors and teeth on both lateral and medial mandibular margins.
Copyright © 1988 Wiley-Liss, Inc.