MECHANORECEPTORS AND CHEMORECEPTORS AND THEIR POSSIBLE ROLE IN NEST LOCATION BEHAVIOR OF SYMPIESIS-SERICEICORNIS (HYMENOPTERA, EULOPHIDAE)

Observations of behavioral interactions between the parasitoid Sympies is sericeicornis Nees (Hymenoptera: Eulophidae) and the leafmining hos t Phyllonorycter malella (Gerasimov) (Lepidoptera: Gracillariidae) sho w that the parasitoid reacts to vibrational signals emitted by the mov ing larva. In this study we used electron microscopy to investigate th e sensilla morphology of the parasitoid S. scriceicornis. Classificati on of the sensilla allowed us to discuss functional aspects in the wid er framework of vibrational communication in this system. Tile antenna e of the female parasitoid has 4 types of sensilla. Two are chemorecep tive, mechanoreceptive, and thermohygroreceptive. Several types of tri choid sensilla are found at the antennal tip. Male and female parasito id are dimorphic for the antennal tip. Of the tarsus structures, only the pretarsus and the last tarsomeres of female and male parasitoids w ere in contact with the leaf surface. The tarsomeres were covered by 3 types of mechanoreceptors. At the pretarsus, sensilla were found on t he manubrium and claws. The claws had contact chemoreceptors and mecha noreceptors, and the manubrium had only mechanoreceptors, a trichoid s ensillum, and campaniform sensilla. The membranous arolium had no sens illa, but could be invaginated and evaginated. This evagination proces s influenced the position of all sensilla on the pretarsus. The sensil la inventory was compared with other parasitoid species. Eulophid para sitoid species share the same basic inventory of sensillae. The role o f different sensilla is discussed in detail with respect to functional aspects for host location behavior. of S. sericeicornis and other par asitoid species.