Chemical communication in heliothine moths

1.	Responses of single olfactory receptor neurons to pheromones were recorded with tungsten microelectrodes on the antennae of male Helicoverpa (Heliothis) zea. Recordings were obtained from the male specific sensilla trichodea type 1.
2.	More than half (49/91 units) could be classified as olfactory receptor neurons, 35 of which were selective for pheromone components of the heliothine moths H. zea and Heliothis virescens. The majority (31/35) were most responsive to the principal component (Z)-11-hexadecenal (Z11-16AL). The other 4 were tuned to (Z)-9-tetradecenal (Z9-14AL), which is a pheromone component in the sympatric species H. virescens, and also interrupts attraction of H. zea males.
3.	The specificity and sensitivity of these neurons were similar to the corresponding neurons in H. virescens, suggesting homologous populations of neurons in the two species. No other neurons selective for other pheromone compounds were identified.
4.	Receptor neurons of both types (tuned to Z11-16AL and Z9-14AL respectively) showed variations in temporal response characteristics. Some responses showed a pronounced phasic spiking component, a rapid decay, and return to background activity after stimulation. Other responses were more prolonged, far outlasting the stimulation period. Phasic neurons also followed short, rapid stimulus pulses better than tonic neurons, suggesting that they may encode different features of an intermittent pheromone plume.