Repeatability of Aggressiveness against Con-and Heterospecific Prey in the Predatory Mite Neoseiulus californicus (Acari: Phytoseiidae)

Abstract

Repeatability, (the consistency with which a given trait is expressed) of aggressiveness against prey (attack latency) in gravid females of the predatory mite Neoseiulus californicus (McGregor) was examined. In two experiments, prey - conspecific individuals, the onion thrips Thrips tabaci (Lindeman), and the two-spotted spider mite Tetranychus urticae Koch- were repeatedly offered in various no-choice vs. choice situations. Throughout the first experiment, the pr edators were offered conspecific larvae twice, alone and then together with Te. urticae . In a second experiment, the predators were alternately offered Te. urticae and Th. tabaci within choice vs. no-choice situations. Latency to the first successful attack (resulting i n death and consumption of prey) was recorded as aggressiveness. In the first experiment , Pearson’s r indicated that the predators were consistent in aggressiveness against conspecific prey. Additionally, latency to attack conspecific larvae and Te. urticae were strongly correlated when the former were offered alone and the latter offered together with conspecific larvae. In the second experiment, aggressiveness against spider mites and thrips was inconsistent, non- repeatable and varied among contexts. However, Te. urticae was attacked more quickly when offered second, following the first prey Th. tabaci than when offered as the first prey. Both experiments, in concert, suggest that th e level of behavioral consistency of N. californicus in aggressiveness against prey is strongly context -dependent. Further in- depth studies are needed to determine which foragin g traits, (and why and under what circumstances) are more repeatable than others. Keywords: Aggressiveness, Cannibalism, Consistency, Neoseiulus californicus , Repeatability.