PULSED PHEROMONE STIMULI AFFECT THE TEMPORAL RESPONSE OF ANTENNAL RECEPTOR NEURONS OF THE ADULT CABBAGE-LOOPER MOTH

Male cabbage looper moths, Trichoplusia ni (Hubner) (Lepidoptera: Noct uidae), fly upwind in response to pheromone blends produced and releas ed by calling conspecific females. Specialized sensilla on the male an tenna contain sensitive, highly specific olfactory receptor neurones w hich respond to constant olfactory signals, with a phasic-tonic patter n of action potential discharge. Olfactory stimuli in nature are not u niform. They are thought to consist of pulses of odours whose distribu tion is shaped by wind and local environmental features. We begin to e valuate this natural situation by stimulating pheromone-sensitive sens illa with short (200 ms) paired pulses of the major component of the f emale's pheromone blend, (Z)-7-dodecen-1-ol acetate (Z-7,12:AC). Diffe rent stimulus protocols in which the pulses were separated from each o ther by varying intervals were evaluated. The interval between pulses had a large effect on the phasic component of the response. Intervals between pulses as short as 30 ms reduced the response to a second puls e by >50%. When the intervals between pulses were longer than 3 s, sig nificant differences were not seen between the responses to the first and second pulse. Implications for male orientation in natural, female -produced, pheromone plumes are discussed.