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Estimating Prey Consumption in Natural Populations of Harmonia axyridis (Coleoptera: Coccinellidae) Using Production of Feces

Abstract Production of feces (PF) is a useful proxy indicating quantity of ingested food. Although influenced by many uncontrolled factors PF provides insight into food consumption under natural conditions. In Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) variation in PF was investigated in populations of various hostplants at localities of central Bohemia (50N, 14E), throughout the season of 2016. The adults collected from these hostplants were starved for 48 h at standard conditions, and dry mass of feces produced during this period was measured. Despite enormous differences in PF among individuals, significant variation over the season occurred in average PF of both males and females. PF increased with abundance of aphids and was significantly greater in females than males. Gravidity, as manifested through oviposition within 48 h after capture, was associated with increased PF, while hostplant and color morph did not affect variation in PF among individuals. From PF as measured in this study, it can be estimated that at sites hosting abundant aphid populations H. axyridis (as an adult male or female) may consume 19 (male) to 45 (female) aphids per day (assumed body length 1mm). In the absence of aphids, adults may consume one to nine individuals of alternative prey per day (body length 1–2 mm).