A novel type of counterattack against predatory thrips in Schizotetranychus brevisetosus (Acari: Tetranychidae)
2022
Ito, Katsura | Ioku, Yuta
Numerous predators prey on herbivorous arthropods, and some prey species have evolved counterattacks against predators (predator–prey reversal). Counterattacks often entail a lethal cost but increase the fitness of the attacking individuals and their nearby relatives. Spider mites (Acari: Tetranychidae) live on leaf surfaces, and some live in aggregations with relatives in a web nest. Counterattacks have been studied in Stigmaeopsis species, but have rarely been studied in other web-nesting species. We investigated counterattacks against predatory thrips, Scolothrips takahashii Priesner, by Schizotetranychus brevisetosus Ehara, which inhabits Quercus glauca L. (Fagaceae). Here, thrips nymphs introduced onto a mite-infested piece of leaf quickly entered the nest but were driven out by females using their stylets. However, in another experiment, we could not find a difference between treatments (10 adult females per leaf or none per leaf) in the number of eggs consumed at 48 h, probably because the thrips repeatedly re-entered the nest. Additionally, we did not detect a significant effect of web presence on predation. Although the defensive effect is undetectable, this study shows that S. brevisetosus counterattacks occur both inside and outside the nest, and the latter especially is the first report of such behaviour in Acari.
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