Tetranychus urticae (Acari: Tetranychidae) male defensive behavior against Phytoseiulus persimilis (Acari: Phytoseiidae)

The nature of spider mite counterattack and defensive behavior and their effects on predatory mites have only been investigated in social species. Here, we have examined the defensive success of Tetranychus urticae Koch (Acari: Tetranychidae) male individuals in the presence of Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseiidae) juveniles. We recorded the number of T. urticae eggs eaten (killed) within three days along with monitoring the predator (dead/alive) status. The defensive behavior of T. urticae male was considered as success when the predator had consumed less than 50% of the prey eggs and was killed at the end of the experimental period. Our main hypothesis was that introducing an additional male would increase the defensive success rate. Results showed that the success rate was significantly higher in the patches with two T. urticae male individuals compared to one. No significant difference were observed among the egg-eating (killing) rate within the three consecutive days of experiment in patches with one male, while in the treatments with an additional male, the egg killing rate of the third day was significantly higher than that on the first day. We also hypothesized that male T. urticae with significant higher rate of defensive success should be morphologically different in comparison with the defeated ones. We found no significant differences in the length of chelicera, first leg and body (length and width) between the successful versus defeated males. We concluded that T. urticae can attack the predator, but the weapon by which the success happens remained unclear.