THE SIGNIFICANCE OF MAJOR PHEROMONE COMPONENTS AND INTERSPECIFIC SIGNALS AS EXPRESSED BY RECEPTOR NEURONS IN THE ORIENTAL TOBACCO BUDWORM MOTH, HELICOVERPA-ASSULTA

Receptor neuron specificities for intra- and interspecific chemical si gnals were determined in males of Helicoverpa assulta, by testing sing le neurons for twelve heliothine produced compounds and two chemical a nalogues. Three types of receptor neurons were identified in the male specific sensilla trichodea type 1. 1. One large group of neurons (29 out of 63) was tuned to the major pheromone component (Z)-9-hexadecena l, in contrast to results obtained previously in a related species, wh ere the information from this compound seems to be mediated via neuron s tuned to (Z)-9-tetradecenal. 2. Another group of neurons (28/63) was tuned to (Z)-9-tetradecenal which is not produced by the conspecific females. These neurons and those tuned to the major pheromone componen t, always appearing together, are probably located in the same sensill um. Their large number suggests that (Z)-9-tetradecenal mediates an im portant message in this species, probably causing interspecific interr uption. 3. The third group of neurons (6/63) was tuned to the second p rincipal pheromone component (Z)-11-hexadecenal. These neurons showed similar specificities as the corresponding type of neurons in related species, indicating a conservation of their membrane receptors through evolution. In contrast, the (Z)-9-tetradecenal receptor neurons in H. assulta showed a different specificity than their counterparts in the related species, suggesting that their receptor proteins have evolved differently.