Prey Preference of Predatory Larvae of Episyrphus balteatus (Diptera: Syrphidae): A Function of Variable Prey-Host Plant Combination

Episyrphus balteatus (De Geer) (Diptera: Syrphidae) larvae are polyphagous predators of aphids (Hemiptera: Aphididae) and play an important role in their biological control. This study examined the prey preference of E. balteatus larvae among different aphid-host plant combinations and evaluated the influence of lingering aphid cues on larval choice. Four treatments were tested: Lipaphis erysimi (Kaltenbach) on cabbage (Brassica oleracea) (Family: Brassicaceae), L. erysimi (Kaltenbach) on mustard (Brassica nigra) (Family: Brassicaceae), Aphis gossypii Glover on chamomile (Matricaria chamomilla) (Family: Asteraceae), and Aphis nerii Boyer de Fonscolombe on milkweed plant (Calotropis gigantea) (Family: Apocynaceae). In a four-choice arena, second instar larvae (n=33, starved for 24 hours) showed statistically significant prey preference. L. erysimi on cabbage was most preferred, while A. nerii was the least chosen, possibly due to the presence of cardenolides. In a separate experiment, larval attraction to previously aphid- infested leaves (aphids removed) was compared with uninfected leaves. Larvae (n=30) preferred previously infested leaves in 73.3% of trials, and the difference was statistically significant based on a goodness of fit test, indicating attraction to residual cues such as honeydew left by aphids on the leaf surface. Results highlight that prey selection in E. balteatus larvae is shaped by both prey species and host plant, as well as residual chemical signals. These findings improve understanding of syrphid larval foraging ecology and support their application in integrated pest management programs.