Captures of the olive fruit fly Bactrocera oleae on spheres of different colours

Alighting and capture of wild olive fruit flies, Bactrocera oleae (Rossi) ( Diptera, Tephritidae), on spheres of seven different colours was studied on Chios island, Greece. The 70-mm-diam plastic spheres, coated with adhesive , were suspended on olive trees. Yellow and orange spheres trapped the grea test number of males while red and black spheres trapped the greatest numbe r of females. White and blue spheres were the least effective for both sexe s. Peak captures occurred in the late afternoon and especially around sunse t. Since mating takes place in the last hours of the photophase, the increa sed captures during that period may be related to the sexual behaviour of t he fly. When red spheres were assessed against glass McPhail traps baited w ith 2% ammonium sulphate, which consist a standard tool for monitoring the olive fruit fly in Greece, there were no significant differences in male ca ptures. However, spheres trapped almost three times as many females as McPh ail traps. The possible mechanisms underlying colour discrimination, the mo tivation of alighting flies and the possible use of red spheres for monitor ing and controlling B. oleae are discussed.