1IACR Rothamsted Experimental Station, Harpenden, Herts. AL5 2JQ, UK.
2Institute of Agricultural Entomology, Perugia University, Borgo XX Giugno, 06121 Perugia, Italy.
The semiochemistry of the cabbage stem flea beetle, Psylliodes chrycocephala (Coleoptera: Chrysomelidae) is being investigated as part of a study aiming to formulate alternative control strategies for this economically important pest species. In time-lapse video observations, males spent significantly more time in the vicinity of an enclosure containing a female than one containing a male. Ultrastructural investigations have revealed a female-specific gland on the pygidium. We postulate that this is the source of the attractant. After mounting a female, males vigorously circle their antennae over the head and thorax of the female for approximately five minutes, during which time female activity decreases. Antennomeres 6-10 of males were found to contain a gland that was absent from females. This gland was only actively secretory in post-diapause (reproductively active) males. We hypothesise that this gland is the source of an aphrodisiac pheromone that pacifies the female, increasing the likelihood of successful insemination. Further behavioural studies are underway to test these theories.