Agonistic Behavior in Male Spider Mites: Factors Affecting Frequency and Intensity of Fighting1

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Abstract
Agonistic behavior in male spider mites ( Tetranychus urticae Koch) was found to be mediated by apparent chemosensory cues signifying the onset of ecdysis in quiescent (molting) females. Newly quiescent females were only weakly defended, while females close to emergence elicited a marked increase in both the incidence and intensity of fighting. Freshly shed exuviae and webbing had no significant effect on male response. As aggressive encounters increased in intensity, the chances of a guarding male successfully defending a female were reduced. Loss of a female was most common when fighting occurred at high male density. Guarding males were less aggressive in crowded conditions, tending to cling tightly to a quiescent female instead of attacking intruders. These behavioral patterns appear to have arisen from selective pressures for optimum time investment in guarding.