Predation effect of Eocanthecona furcellata on Bombyx mori larvae

Currently, Lepidoptera pests like Spodoptera litura and Spodoptera frugiperda are the main food source for Eocanthecona furcellata when it comes to large-scale artificial feeding operations. However, using pest insects as food sources inevitably increases the risk of pest migration, invasion, and dispersal hazards when commercially packaging E. furcellata and transporting them with feed over long distances to release sites. In this study, we specifically investigated the predation behavior, predation function and searching effect of E. furcellata all developmental stages for 2^nd~4^th instars Bombyx mori larvae as food. The results demonstrated that E. furcellata at all developmental stages could successfully attack and consume B. mori larvae through solitary predation or collective hunting. Predation rates increased with B. mori larval density until reaching a plateau at higher prey densities. The functional responses conformed to the Holling Ⅱ disc equation model, with predation capacity positively correlated to predator instar. The second-instar E. furcellata exhibited a maximum daily predation numbers on second-instar B. mori larvae were 24.042. Adults showed the highest predation capacity, with maximum daily predation numbers were 42.1553, 18.5510, and 20.5951 individuals for second, third, and fourth-instar B. mori larvae, respectively. Searching efficiency was negatively correlated with prey density. Under equivalent prey instar and density, higher-instar E. furcellata generally displayed greater searching efficiency than those of younger instars, and all predator stages showed higher searching efficiency when preying on younger B. mori larvae compared to older ones. In conclusion, E. furcellata can effectively feed on nutrient-rich B. mori larvae, significantly enhancing field release safety. This study provides theoretical guidance for selecting appropriate B. mori larval instars and quantities in mass-rearing systems based on predator developmental stages, also proposing novel approaches for diversifying B. mori resource utilization.