CHEMICAL ECOLOGY Male and Female Antennal Responses in Heliothis virescens and H. subflexa to Conspecific and Heterospecific Sex Pheromone Compounds

To determine whether Heliothis virescens and H. subflexa, two closely related sympatrically occurring species, differ in their antennal responses to conspeciÞc and heterospeciÞc pheromone compounds, we recorded electroantennogram (EAG) responses of male and female antennae of both species to eight different compounds loaded on Þlter paper dispensers. If antennal responses were found to differ in the two species, EAG-recordings from F1 hybrids and backcrosses between these species could be used in developing an understanding of the genetic architecture of variation in olfactory signal perception. However, all compounds elicited EAG responses in all male antennae tested, and no quantitative differences in response were found between the two species, except for the response to 1 mg (Z)-11-hexadecenol (Z11Ð16:OH), which elicited larger EAG responses in H. subflexa than in H. virescensmales. This difference is consistent with the idea that this pheromone component is less important in the biology ofH. virescens. Female antennae of both species were less responsive to the major sex pheromone compound, (Z)-11-hexadecenal (Z11Ð16:Ald), than male antennae; 10 g Z11Ð16:Ald, which elicited strong EAG responses in males, produced female EAGs similar to control puffs of air. However, higher doses of Z11Ð16:Ald elicited signiÞcant EAG responses in female antennae of both species. Female antennae of both species also responded to most other pheromone compounds, except Z11Ð16:OH. These results support the hypothesis that autodetection of sexpheromonesoccurs in femalesofbothH.virescens andH. subflexa.Whether femalesbehaviorally respond to any, or to combinations, of these compounds remains to be elucidated.