MORPHOLOGY AND ULTRASTRUCTURE OF ANTENNAL SENSILLA OF THE PARASITOID, TRYBLIOGRAPHA-RAPAE (WESTW) (HYMENOPTERA, CYNIPIDAE)

Each antenna of female Trybliographa rapae Westw. (Hymenoptera : Cynipidae) consists of 13 segments: a scape, a pedicel and 11 flagellar segments (F1-F11). Trichoid sensilla are present on every segment and total approximately 1000 per antenna. The number of trichoid sensilla increases on each segment from the scape to segment F6, then declines slightly with each segment up to F10 before increasing markedly on segment F11. There are approximately 200 placoid sensilla per antenna, distributed evenly among segments F4 up to F10 but increasing sharply on F11. Coeloconic sensilla occur singly on every segment from F4 up to F10 and 2 are present on F11; thus, there are usually 9 coeloconic sensilla per antenna. Ultrastructural evidence suggests that the trichoid sensilla are mechanoreceptors whereas the presence of multiple pores and multiple neurones identifies the placoid sensilla as olfactory chemoreceptors.