Boletín de la AeE

Coplera occidentalis Mués., a Nearctic pupal parasitoid of the walnut husk fly, Rhagoletis completa Cress., is reared in the laboratory for biológica! control triáis against the adventive populations of this fly, which appeared in Italy at the beginning of the 90s.

Preliminary investigations carried out by scanning and transmission electrón microscopes on male and female antennal structures allowed us to map and describe several types of sensilla and glands. .Ajitennal sensory and secretory structures likely involved in mating behaviour and host recognition have been further studied.

Male antennal glands and female chemo-sensilla seem to be connected in sexual behaviour. Male antennae have two glands on A3 and A4 with typical reléase structures on the ventral part of the corresponding antennomere: a peg-like process on A3 and a porous carina on A4. Female antennae bear chaetica sensilla with fluted hair (uniporous sensilla, probably gustatoiy) on the ventral side of the A7-A12. Different phases have been observed during mating. In the first phase, (precopulation) the male touches the female antennae to be accepted, then they mate (copulation). After copulation, the male again places his antennae in contact with the female antennae (postcopulation). The position of antennal structures and antennal movements during the mating phases suggest that male glandular secretion is probably used in sexual recognition and it is detected by female gustatory sensilla.

Female short sensilla basiconica (multiporous sensilla, probably gustatory) seem to be the only antennal structure involved in host recognition. These sensilla, arranged in a patch on the ventral side of A7-A12, vary in number from about 12 at A7, to about 80 at the distal antennomere. Before ovipositing, the female drums host pupae with distal antennomeres where multiporous sensilla are located.

Bioassays have been carried out to highlight the role of these sensory and secretory structures during the mating and the host recognition.