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)

Abstract

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 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 µg), 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 Z98022

Visual ground pattern modulates flight speed of male Oriental fruit moth Grapholita molesta

“…Honeybees also fly faster over axial stripes running parallel to the tunnel walls and the mean direction of flight than when they fly over a checkerboard pattern, which affords strong transverse cues not present in the axial stripes (Baird et al , , ). Thus, the axial pattern does not provide contrast cues in the direction of flight, and the bees' flight speed is regulated by other visual cues in the experimental environment, similar to the results for lightbrown apple moth (Tortricidae) in a flight tunnel (Foster & Howard, ) and the results of the present study with male OFM flying in the tunnel without an experimental ground pattern. Male gypsy moths, Lymantria dispar (Lepidoptera: Erebidae), flying tethered to a thrust meter in a modified ‘barber pole’ flight tunnel, also generate the maximum forward thrust when they view the surroundings through an insufficient region of the eye (Preiss, ).…”

“…In a quantitative test of Kennedy's () optomotor servo mechanism hypothesis to regulate flight speed (Kuenen & Baker, ), free‐flying male Oriental fruit moths (OFM) Grapholita molesta Busck (Tortricidae) and Heliothis virescens (Noctuidae) flying upwind toward a pheromone source at different heights above the ground pattern are observed to increase their net ground speed with increased flight height as predicted, although the moth's flight speed does not increase sufficiently to maintain a constant visual angular velocity of image motion across their retinas. Similar results are reported in other studies in which male insects were flown in a pheromone plume at two different heights over a constant ground pattern: lightbrown apple moths Tortricidae: Epiphyas postvittana (Foster & Howard, ) and larger grain borer beetles Bostrichidae: Prostephanus truncatus (Fadamiro et al , ). In both cases, the insects fly faster at higher elevations, although the image of the ground pattern is not maintained at a constant visual angular velocity.…”

Egomotion estimation with optic flow and air velocity sensors

“…If odor tracking insects were flying so as to maintain a preferred optic flow across their retinas, then it would be expected that the ground vector would increase proportionally with odor plume altitude. However, a proportional relationship between the ground vector and odor plume altitude has never been observed for any odor tracking insect [moths Heliothis virescens and Grapholita molesta (Kuenen and Baker 1982), Epiphyas postvittana (Foster and Howard 1999), beetles Prostephanus truncatus (Fadamiro et al 1998), or wasps Microplitis croceipes (Zanen and Cardé 1996)]. Furthermore, during odor tracking, an insect must be able to resolve the wind vector from the air vector, thus, from (1), it must also be able to determine its ground vector.…”

“…In several insect species, a male insect locates a mate by flying upwind when it smells the sex-attractant pheromone released by a female of the same species (Kennedy and Marsh 1974). The speed at which they progress upwind while tracking an odor (i.e., the upwind component of the ground vector) is nearly the same in any wind speed, thus these insects do not fly at a preferred airspeed (Willis and Arbas 1991;Zanen and Cardé 1996;Foster and Howard 1999). If odor tracking insects were flying so as to maintain a preferred optic flow across their retinas, then it would be expected that the ground vector would increase proportionally with odor plume altitude.…”

Behavioral responses of Chrysomya megacephala to natural products

“…There are many advantages of the wind tunnel over other methods, such as allowing for an odor gradient to be created along the line of the air flow in the wind tunnel, which mimics the way odors form and disperse in nature. Using these odor gradients formed in a wind tunnel, an insect can use positive anemotaxis for navigation toward the odor source in the same way that it might in the field (Foster and Howard 1999). In addition, advantages in using laboratory wind tunnel studies over field studies in the initial stages of olfactory attractant identification include greater control of the variables that modulate insect response, higher discriminating power, and the ability to conduct experiments throughout the year or during inclement weather (Clements 1999).…”