Fine structure of sensilla on the ovipositor of the tephritid fly Urophora affinis

There are four types of sensilla on the ovipositor blade of Urophora affinis Frauenfeld, one more than was observed on three other species of fruit flies studied by other authors. Three of the types, uniporous gustatory pegs, campaniform organs, and tactile short hairs are common to the four species and generally are in similar positions on the blade. The fourth, uniporous gustatory plates, were noted in U. affinis only. The chemosensilla are innervated by three chemosensory dendrites that terminate below the pore and a mechanosensory dendrite with a tubular body that is attached to a basal cuticular apodeme of the covering cuticle. The dendritic tubular bodies of the campaniform organs and tactile hairs terminate parallel to the surface in a right-angular bend, where they are attached to basal apodemes of the covering cuticle. The chemosensilla and tactile hairs have individual outer and inner sheath cells, but the campaniform organs have individual inner sheath cells only. The part of the ciliary dendritic segment that is encased by the dendritic sheath passes through an epidermal cell, often with several sensilla sharing the same epidermal cell in place of an outer sheath cell. The role of these sensilla during oviposition is discussed.