Surrogate species in pesticide risk assessments: toxicological data of two Brazilian stingless bees species.

The lack of toxicological data on pesticide use in native bee species and the impact of adjuvants in commercial products are considered gaps in the regulatory process and research literature. Stingless bees are pollinators of tropical and subtropical distribution. Despite being highly eusocial like Apis mellifera, differences between life-history traits make these bees more sensitive to pesticides. This research studies the chronic oral toxicity of pesticides on two different species of stingless bees: Scaptotrigona postica and Tetragonisca angustula, both of which are considered surrogate species for pesticide assessment. Three formulated products were analysed: the herbicide glyphosate, the insecticide thiamethoxam, and the fungicide tebuconazole. Medium lethal dose bioassays were performed on worker bees based on the OECD protocols for the model species Apis mellifera with adaptations for stingless bees. The concentration of both herbicide and fungicide exceed  100 μg a.i. and was considered non-toxic. The effect of these products resulted similarly for Apis mellifera due to their working mechanism.For the insecticide, the species Scaptotrigona postica and Tetragonisca angustula presented, respectively, a mean oral lethal dose of 0,0027 μg/ bee and 0,0014 μg/bee  in 24 hours, and in 48 hours of 0,002 μg/bee and 0,00085 μg/bee. This study suggests that stingless bees have greater and different sensitivities to neonicotinoid insecticides, reinforcing the importance of more representative pesticide risk assessments to conserve stingless bees and other native species.