SYNOMONE-INDUCED SUPPRESSION OF TAKE-OFF IN THE PHYTOSEIID MITE PHYTOSEIULUS-PERSIMILIS ATHIAS-HENRIOT

Plant-inhabiting predatory mites in the family Phytoseiidae are known to disperse passively on air currents, In this article we analyse obse rvations on the behaviour that initiates aerial dispersal, the so-call ed take-off behaviour. When starved for 24 hours at 25 degrees C and 3 5% RH, about 80% of the females of Phytoseiulus persimilis Athias-Henr iot became airborne during 10 minute exposure to wind velocities of 2 m s(-1) or higher, However, take-off was suppressed when females were exposed to volatile chemicals emanating from leaves that had been infe sted by two-spotted spider mites (Tetranychus urticae Koch) during one day preceding the experiments. This result is the first unambiguous p roof that phytoseiid mites exert control over take-off. Interestingly, the females of the predator strain under study did not show the chara cteristic upright posture that was hypothesized to be important far ta ke-off in two other species of phytoseiid mites (Amblyseius fallacis G arman and Metaseiulus occidentalis (Nesbitt)). These observations shed new light on the behaviour involved in controlling take-off. It is su ggested that take-off control is exerted mainly via the grasp of the c laws and the adhesive empodia in a way reminiscent of that described f or aphids.