The wood cockroach, Parcoblatta spp., is sexually dimorphic for wing length; females are flightless, with reduced wings, while males' wings extend past the tip of the abdomen and are used in flight. We predicted that female Parcoblatta releases a volatile sex pheromone, attracting the more mobile male. Nymphs of the broad wood cockroach, P. lata (Brunner), were collected from beneath the bark of fallen pine trees in Raleigh, North Carolina, and reared in the laboratory under a 12:12 light:dark photoregime at 27 ± 1ºC. Several days past emergence, females exhibited calling behavior during the scotophase, simultaneously stretching and lowering their abdomens. Solvent extracts and volatile collections from calling and non-calling females were analyzed by electroantennogram (EAG). The EAG amplitude ratio of the test sample to a non-sex-specific odor, (-) bornyl acetate, was quantified using male and female antennae; the male response was divided by the female response, so that an amplitude ratio of >1 indicated the presence of a female-produced, sex-specific pheromone. We found that the first through seventh tergites were the only body parts that elicited a response >1. Activity of the extract increased from age one day to seven days and was lower in mated females than in virgin females of corresponding age. To test whether calling behavior is associated with the release of pheromone, volatiles from calling and non-calling females were collected with a Pasteur pipette packed with Super-Q and placed directly over the abdomen. Volatile collections from calling females elicited higher sex-specific EAG response than collections from non-calling females. Volatile collections were then used in an olfactometer (Y-tube) choice test, in which males preferred volatiles from calling females over those from non-calling females. We conclude that female P. lata produce a sex-specific volatile pheromone that is released through calling behavior.
Species 1: Dictyoptera Blattelidae Parcoblatta lata (broad wood cockroach)
Keywords: pheromone
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