New insight into the antennal chemosensory function of Opius concolor (Hymenoptera, Braconidae)

The presence of taste and olfactory chemosensilla is demonstrated by using both morphological and electrophysiological techniques on antennae of Opius concolor, a parasitoid of tephritid larvae. Observation under the Scanning Electron Microscope revealed the presence of large sensilla trichodea with an apical pore, and of flat plates (sensilla placodea) extending almost th e entire length of each antennomere. By means of currently used electrophys iological techniques, it was possible to record both the gustatory activity generated by sensilla trichodea following contact with KCl 100 mM and sucr ose 100 mM solutions, and olfactory activity probably generated by sensilla placodea in response to volatile stimuli. The analysis of gustatory activi ty showed that each sensillum trichodeum consisted of at least three chemos ensory units. This supports the assumption that in O. concolor single sensi lla may, by providing different spike discharge patterns, which depend on t he quality and intensity of the stimulus, provide the CNS with adequate inf ormation for peripheral discrimination among stimulating chemicals. Study o f the sensory input of O. concolor with electrophysiological techniques may be of great scientific importance for possible applications in biocontrol of the olive fly.