UTILIZATION OF WESTERN FLOWER THRIPS ALARM PHEROMONE AS A PREY-FINDING KAIROMONE BY PREDATORS

The alarm pheromone of the western flower thrips, Frankliniella occide ntalis (Pergande) (Thysanoptera: Thripidae), is present in the droplet of anal fluid produced by second-instar nymphs when attacked by preda tors. Because the anal droplet is used in defense against arthropod pr edators, it was hypothesized that the alarm pheromone (decyl acetate p lus dodecyl acetate) acts as a defensive allomone. This hypothesis was refuted by the demonstration that two predators use the pheromone as a prey-finding kairomone. On a leaf arena, Orius tristicolor White (He miptera: Anthocoridae) increased its rate of turning in response to th e pheromone, and spent 25% of its time within 5 mm of a pheromone sour ce. When given a choice between connected leaf discs containing a pher omone- or solvent-treated wick, Amblyseius cucumeris (Oudemans) (Acari na: Phytoseiidae) spent a greater proportion of time on the pheromone- containing disc, suggesting an arrestment effect.