Antennal sensilla of the generalist parasitoid, Cotesia marginiventris (Hymenoptera: Braconidae): Sexual differences in the abundance and distribution of putative chemosensilla

Cotesia marginiventris (Cresson) is a generalist parasitoid of caterpillar hosts from a wide range of families. Previous research by our group demonstrated antennal response of C. marginiventris to several host-related semiochemicals. As a requisite to our ongoing electrophysiological studies of olfaction in this species, the present scanning electron microscopy study was conducted to determine the abundance, location and distribution of chemosensilla in male and female C. marginiventris. Three major types of sensilla were found on the flagellum of both sexes: sensilla placoidea, sensilla basiconica (I & II) and sensilla trichodea. High-resolution SEM revealed a single pore tip on s. basiconica I and multiple pore presence on the wall of s. basiconica II and elongated s. placodea, possibly suggesting chemoreceptory functions. Significant sexual differences were recorded in the abundance and distribution of s. placoidea and s. trichoidea in C. marginiventris: these sensilla were more abundant on female than on male antennae.