ANTENNAL SENSILLA AND THEIR POSSIBLE FUNCTIONS IN THE HOST-PLANT SELECTION BEHAVIOR OF PHENACOCCUS-MANIHOTI (MATILE-FERRERO) (HOMOPTERA, PSEUDOCOCCIDAE)

Nine different types of sensilla have been identified on the antenna o f the cassava mealybug Phenacoccus manihoti (Homaptera: Pseudococcidae ) with scanning and transmission electron microscopes. Trichoid sensil la, distributed on all segments of the antenna and innervated by a sin gle mechanoreceptive dendrite, have the characteristics of exterocepto rs. A campaniform sensillum located on the pedicel and one basiconic s ensillum on the flagellum have the characteristics of proprioceptors. Coeloconic sensilla, located ventrally on the pedicel and flagellum, r elated to poreless sensilla with inflexible sockets, have the characte ristics of thermo/hygroreceptors. Uniporous sensilla with a mechanorec eptive dendrite (smooth pegs P1 and P2, grooved pegs P3) and multiporo us chemosensilla (grooved pegs P4 and P5), present on the tip of the f lagellum, have, respectively, the characteristics of gustatory and olf actory receptors. The results of this study seem to suggest that the c assava mealybug has sensory equipment on its antennae that can detect, by olfaction and contact, chemicals released by the plant.