How much pollen do solitary bee larvae consume? Or establishing realistic exposure estimates of solitary bee larvae via pollen for the use in risk assessment

Bees foraging in agricultural habitats can be exposed to plant protection products. In order to limit the risk of adverse events to occur a robust risk assessment is needed, which requires reliable estimates for the expected exposure. Especially the exposure pathways to developing solitary bees are not well described and in the currently proposed form rely on limited information. To address this topic, we used a published data set on the volume of pollen solitary bees provide for their larvae to build two scaling models predicting the amount of protein and pollen developing solitary bees need based on adult body weight. We test our models using both literature and experimental data, which both support the validity of the presented models. Using scaling models in the bee risk assessment could complement existing risk assessment approaches, facilitate the further development of accurate risk characterization for solitary bees and ultimately will help to protect them during their foraging activity in agricultural settings.