New Zealand Journal of Zoology abstracts
The effects of source dosage, flight altitude, wind speed, and ground pattern
on the sex pheromone-mediated flight manoeuvres of male lightbrown apple moth,
Epiphyas postvittana (Walker)
S. P. FOSTER
A. J. HOWARD
The Horticulture and Food Research
Institute of New Zealand
Mt. Albert Research Centre
Private Bag 92 169
Auckland, New Zealand
Abstract The flight tracks (plan view) of male
Epiphyas
postvittana flying in a sex pheromone plume in a wind tunnel were recorded.
With increasing source dosages (10, 100, 300 ug), males steered a more upwind
course, with corresponding track angles more upwind, and had smaller intertrack
reversal distances (i.e., they showed less lateral movement). Although net
ground speed tended to increase with increasing source dosage, the effect was
not significant. Increased wind speed (from 20 to 40 cm sec
-1)
resulted in little change in the apparent track of the males, but males
increased their airspeed and steered a course more upwind in response to the
increased downwind push and crosswind drift. Flight altitudes (source suspended
at 5, 12.5, and 20 cm above the floor of the tunnel), had little effect on
most flight parameters, except for ground speed and airspeed, which increased
with increasing altitude, and which in turn resulted in increases in intertrack
reversal distances. Finally, males steered a more upwind course and had a
higher net upwind velocity when flying over a ground pattern of longitudinal
black and white stripes than over a ground pattern of lateral black and white
stripes. Across all treatments, the frequencies of turning back and forth
across the windline were similar. These results are consistent with those
observed in several other species of moths, and suggest that the
pheromone-mediated flight of male
E. postvittana is shaped by optomotor
anemotaxis (the use of visual images to steer a resultant track and ground
speed with respect to the wind) and by a behavioural mechanism that governs the
rhythmic counterturning.
Keywords Lepidoptera; Tortricidae; optomotor anemotaxis;
orientation; behaviour
Z98022
Received 18 June 1998, accepted 19 November 1998
PDF file of entire paper: medium quality (658K); (scanned from paper original: notes about this process)
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