Acarophagous Beetles Associated with Oligonychus yothersi (Acari: Tetranychidae) in Avocado Orchards: Life-History Traits and Responses to Infested-Plant Volatiles and Prey-Derived Odours

The acarophagous beetles Parastethorus histrio (Chazeau) (Coccinellidae) and Oligota pygmaea (Solier) (Staphylinidae) are naturally associated with colonies of the avocado red mite, Oligonychus yothersi (McGregor) (Acari: Tetranychidae), in commercial avocado orchards. However, their demographics and responses to plant- and prey-derived cues remain poorly understood. Volatile profiles vary with herbivore density, plant condition, and environment, but early-autumn volatiles from mite-infested avocado shoots and their effects on these predators remain uncharacterised. We evaluated the development, survival, reproduction and fertility life-table parameters of both predators when feeding on O. yothersi. We also characterised volatile extracts from non-infested and mite-infested avocado shoots collected during early autumn and assessed predator responses to plant volatiles, live-prey odours and prey-derived residues in two-choice olfactometer assays. Both beetles completed their development on O. yothersi, with egg-to-adult survival rates of 86.6% in P. histrio and 90.0% in O. pygmaea. Parastethorus histrio developed more rapidly and exhibited greater female longevity, whereas O. pygmaea showed higher daily and lifetime fecundity. Both predators had higher net reproductive rates than the prey, but their lower intrinsic rates of increase and longer generation times indicated slower population growth per unit time. Volatile profiles differed between non-infested and mite-infested shoots, with limonene predominating in extracts from infested plants. Both predators allocated more time to extracts from mite-infested than non-infested shoots. Their responses to prey-derived cues differed: O. pygmaea responded positively to odours from live O. yothersi females but not to colony residues, whereas P. histrio reduced its allocation to both stimuli. These findings reveal contrasting life-history and host-location strategies in the two predators and support further evaluation of their potential as natural enemies of O. yothersi in avocado orchards. Field studies are required to determine whether these traits translate into predator establishment and effective suppression of mite populations.