Functional responses and diet-dependent fecundity of Stratiolaelaps scimitus (Acari: Laelapidae) preying on western flower thrips pupae (Thysanoptera: Thripidae)

Western flower thrips, Frankliniella occidentalis, remains difficult to manage in crops because their non-feeding pupal stage is largely concealed in the soil, making it unreachable by foliar insecticides and canopy-dwelling natural enemies. The soil-dwelling laelapid mite Stratiolaelaps scimitus is widely used against edaphic pests, but its performance on thrips pupae relative to factitious prey, and the contribution of different life stages to thrips suppression, are still poorly quantified. We first compared no-choice predation and fecundity of adult females offered either thrips pupae or the dried fruit mite Carpoglyphus lactis (male adults), with a starvation treatment as control. S. scimitus females readily attacked both prey types and produced significantly more eggs when food was available than under starvation, but 48 h oviposition did not differ significantly between the two diets, indicating that thrips pupae and C. lactis provided comparable short-term nutritional support. Next, we quantified the functional responses of S. scimitus deutonymphs, adult males and adult females, to thrips pupae across six prey densities (1, 3, 5, 8, 12 or 15 pupae per arena) over 24 h. All tested stages of S. scimitus exhibited a Type II functional response. Adult females had the shortest handling time and highest asymptotic consumption (≈7.6 pupae per day), adult males were intermediate (≈5.8 pupae day⁻¹), and deutonymphs the lowest (≈3.9 pupae day⁻¹). These results confirm S. scimitus as an effective predator of thrips pupae, with mixed-stage populations contributing to pupal mortality, and support current mass-rearing practices on factitious prey for subsequent deployment against this pest in crops.