| MMSC Karunaratne and UKPR Karunaratne
Department of Zoology, University of Sri Jayewardenepura, Nugegoda, Sri Lanka
Abstrsact
The parapheromone, methyl eugenol (ME) (3, 4 dimethoxyalyl benzene), occurring in a variety of plant species, is the most effective known lure attracting the male oriental fruit fly, Bactrocera dorsalis (Hendel). Bioassays were carried out in a wind tunnel under laboratory conditions, to evaluate behavioural responses of male flies to seven concentrations of ME, diurnal pattern of male responsiveness and age of responsiveness to methyl eugenol and the factors influencing the responsiveness of males to ME. Attraction of male flies to ME was assessed by monitoring three behavioural parameters namely the number of flies performing upwind zigzagging anemotactic flights over at least 50cm to the ME source, total number of flies landing on the source and the total number of flies moved into the upwind section of the wind tunnel after 20 minutes. The responsiveness of males to ME increased with the increase of the concentration, 0.0001µl eliciting the lowest and 5.0µl producing the highest attraction in males. All the males which were attracted exhibited a feeding response and no other behavioural response was observed. Male responsiveness to ME was not uniform throughout the day. The responses were highest during the morning (82.6%), declined to a lower level in the afternoon (41.8%) and then dropped markedly at the ‘dusk’ period (11.4%). This decline in response to ME suggested an inverse relationship to the time of peak mating activity in the male. Male responsiveness to ME was found to be age-dependent. The response to the attractant increased with the age of the flies indicating a relationship between responses to ME and sexual maturity of the flies. No significant responses were evident when males were 1, 3 and 5 days old. Males were strongly attracted to ME by the time they were 10d-old and the highest attraction was observed in 15d-old males. Attraction to ME was still considerably high even when they were 25 and 30d-old.
Key words: Bactrocera dorsalis, methyl eugenol, upwind anemotaxis, male responsiveness
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