COMPARATIVE EFFECTS OF FORM, COLOR, AND PHEROMONE OF 2-SPOTTED SPIDER-MITE QUIESCENT DEUTONYMPHS ON MALE GUARDING BEHAVIOR

Effects of form, colour, and pheromone of twospotted spider mite, Tetr anychus urticae (Koch), quiescent deutonymphs on adult male guarding b ehaviour were tested independently and in combination using no-choice and sequential-presentation bioassays. Significantly more males approa ched yellow stimuli sources than non-yellow sources in all bioassays, suggesting that males orient visually to yellow carotenoid pigments of quiescent deutonymphs. The form and extract (pheromone) of quiescent deutonymphs did not increase male approach frequency. All three cues e licited male arrestment; contrasts of 2 x 3 factorial bioassay data sh owed that male tactile and/or visual perception of form increased arre stment frequency more than did contact chemoperception of extract, whi le extract perception caused more arrestments than did visual percepti on of colour. All three cues prolonged arrestment duration and increas ed frequency of intermale conflicts near stimuli sources, but form had greater impact than did other cues on the numbers of conflicts observ ed during coguarding incidents. Significant interactions among stimuli were observed, indicating that presence of multiple stimuli had a syn ergistic effect on the duration of male response. Males approached and were arrested by all three stimuli combined as often as by quiescent deutonymphs, but arrestments caused by quiescent deutonymphs were long er than those elicited by artificial stimuli. This difference suggests that either additional cues or differences in pheromone release rates are involved in eliciting and prolonging male T. urticae guarding beh aviour.