Morphological characteristics of antennal sensilla in the European cornborer Ostrinia nubilalis (Lepidoptera: Pyralidae).

The European cornborer antenna is filiform in both sexes, but exhibits a substantially larger diameter in the males. On the antenna of both sexes, the following sensillum types were characterized: sensilla trichodea, s. basiconica, s. auricillica, s. coeloconica, s. chaetica and s. styloconica. Long dorsal bristles were of a chaetic type. An intermediate trichoid/basiconic type was found in low numbers on the ventral part of the antenna. In the male, three different morphological types of s. trichodea were observed, having one, two or three sensory cells, correlated with different dimensions of the hair. The s. trichodea with three sensory cells are most common in the basal part of the antenna, while sensilla with two cells are mainly found distally. Trichodea with one sensory cell are more evenly distributed over the length of the antenna. All cells present in the different s. trichodea respond to sex pheromone components or to a behavioural antagonist in electrophysiological sensillum recordings. S. basiconica and s. auricillica had 2-3 sensory cells, and a probable olfactory function. Sensilla coeloconica, also with a putative olfactory function, contained 3-5 sensory cells. S. chaetica of the taste/tactile type possessed 4 + 1 sensory cells. S. styloconica comprised three sensory cells with possible functions as thermo- and hygroreccptors.