Microbe-free feast: beetle larvae increase their consumption when eating leaves without epiphytic microbes

Abstract Foliar insects inevitably ingest microorganisms residing both on the surface and within the internal tissues of the leaves they consume. Among these, epiphytes – microbes inhabiting the leaf surface – are the first to interact with the insects. While some studies have examined the impact of specific epiphytic bacterial strains on insect performance, the role of the entire epiphytic community remains largely unexplored. In this study, we manipulated the presence/absence of the epiphytic community on Datura inoxia leaves and evaluated its effect on the performance of its specialist herbivorous insect Lema daturaphila . Removing the entire epiphytic community affected larval survival, but this effect varied over time. A significant difference was observed only in December, when larvae feeding on leaves without epiphytes experienced a reduced risk of mortality. We also found that larvae feeding on leaves without epiphytes consumed more foliar tissue but were less efficient compared to those eating control leaves. In addition, larvae growing in December were lighter, consumed less, developed more slowly, but showed higher feeding efficiency and adult mass compared to February. Overall, our findings suggest that the epiphytic community associated with Datura inoxia increases the feeding efficiency of its specialist insect, Lema daturaphila .