Ultrastructure of the contact chemoreceptor sensilla of Chrysops caecutienscaecutiens L. (Diptera, Tabanidae)

Contact chemoreceptor sensilla of females of C. caecutiens were studied using transmission electron microscopy and scanning electron microscopy, and compared to those of Tabanus bromius and Hybomitra montana. The trichoid labellar sensilla are comprised of 3-5 receptor cells that have a ciliary zone, basal bodies and rootlets in their peripheral processes. The trichoid sensilla invariably included one mechanoreceptor cell with a peripheral process ending in a tubular body. Branching of the peripheral processes of receptor cells was observed in the cuticular zone of some of the trichoid sensilla. The taste sensilla contained 4 cells: trichogenic, tormogenic, accessory and internal; the internal cell secretes building material for the scolopoid membrane of the peripheral processes.