Effect of pollen consumption on development and intraguild predation of two predatory Coccinellidae

Many omnivorous predaceous coccinellids consume both pests like aphids and a range of plant-derived foods including pollen. It is critical to understand how plant-derived food like pollen could affect the fitness and interspecific interactions of predaceous coccinellids. This study investigated the effect of pollen consumption on the development, reproduction and intraguild predation (IGP) of two naturally co-existing aphidophagous ladybirds, Harmonia axyridis and Propylea japonica. Both species were provided with three diets including a moist canola pollen, the aphid Myzus persicae, or moist canola pollen together with aphids. The 1st instar larval of both H. axyridis and P. japonica could not survive and develop to the next larval stage when supplied with water alone. When fed on pollen only, 53 % of the H. axyridis larvae and 25 % of the P. japonica larvae successfully developed to adult. Both species exhibited an elongated development time, shorter larval body length and lower adult body weight than when offered with aphids and the mixed diet. In addition, P. japonica could not reproduce when fed on pollen alone. Interestingly, when pollen was provided as additional food, the overall IGP between larvae of H. axyridis and P. japonica was significantly reduced compared with water control or aphid as food alone. The results of this study indicated that pollen not only supports the survival of H. axyridis and P. japonica when prey is scarce, but also could benefit the co-existence of these species. For future study, it is necessary to investigate how pollinivory could benefit the fitness and biological control potential of H. axyridis and P. japonica under field conditions.