Current status of toxicological research on stingless bees (Apidae, Meliponini): Important pollinators neglected by pesticides' regulations.

Stingless bees (tribe Meliponini), comprising over 600 known species within the largest group of eusocial bees, play a critical role in ecosystem functioning through their pollination services. They contribute to the reproduction of numerous plant species, including many economically important crops such as cacao, coffee, and various fruits. Beyond their ecological significance, stingless bees hold cultural and economic importance for many native and rural communities, where they are managed for their honey, pollen, and propolis for nutritional and health purposes. The overwhelming majority of studies on pesticide toxicity and risk assessment on bees are conducted on the model species Apis mellifera in the United States and Europe, where stingless bees are absent. In May 2023, the European Food Safety Authority (EFSA) published its revised guidance document on the risk assessment of plant protection products (PPPs) for bees, including, beyond honey bees, other bee species from Bombus and Osmia genera. Despite the Meliponini widespread distribution in tropical and subtropical regions, the impact of pesticides on stingless bees remains largely unexplored. Here, we present a systematic review of stingless bee toxicological studies which highlights a substantial knowledge gap. Up to October of 2024, only 144 research articles on the effects of pesticides on Meliponini had been identified, 80 % of those were conducted in a single country (Brazil). The number of bee species and PPPs tested is extremely low, with just five species accounting for almost 50 % of the collected data and only 79 PPPs tested, among which biopesticides were the most common. Concerning the experimental methodologies, there is a significant lack of studies focusing on chronic exposure and field assays, as well as a scarcity of studies focusing on sublethal effects. Furthermore, we pinpoint to areas where research is needed for the development of risk assessment guidelines to protect these vital pollinators.