Stage-Dependent Predation by Scymnus (Scymnus) folchinii Against Myzus persicae: Functional Response and First-Instar Prey Sharing

Small scymnine coccinellids, including many Scymnus species, are common aphid predators, but stage-specific feeding data are still limited for many species. We investigated feeding behavior, first-instar prey sharing, stage-specific consumption, and functional responses of Scymnus (Scymnus) folchinii (Canepari) on third-instar Myzus persicae nymphs on chili pepper seedlings. Larvae showed feeding behavior consistent with extra-oral digestion, whereas adults consumed aphids by direct mastication. In the single-prey first-instar assay, prey sharing occurred in all 15 arenas; the period during which two or more larvae fed on the same aphid lasted a median of 31.0 min and accounted for 84.8% of the observed feeding period. Aphid consumption varied with predator stage, exposure time, and initial aphid density. At the highest tested density of 16 aphids, third- and fourth-instar larvae and adults left few aphids alive after 24 h in the seedling micro-arena. Logistic regression diagnosed Type II responses only for adults at 1 h, whereas AIC-based model comparison selected Rogers’ Type II in 15 of 18 stage-by-duration combinations. Short exposures indicated higher attack rates and shorter handling times in fourth instars and adults, whereas longer exposures were affected by prey depletion and satiation. These results show clear stage dependence in aphid consumption by S. folchinii and justify further testing on larger plants and under field conditions.