Sensitivity of the Neotropical Solitary Bee Centris analis F. (Hymenoptera, Apidae) to the Reference Insecticide Dimethoate for Pesticide Risk Assessment.

Currently, only Apis mellifera species is used in environmental regulation to evaluate the hazard of pesticides to pollinators. The low representativeness of pollinators and bee diversity in this approach may result in insufficient protection for the wild species. This scenario is intensified in tropical environments, where little is known about the effects of pesticides on solitary bees. Here, we aimed to calculate the medium lethal dose (LD 50 ) and medium lethal concentration (LC 50 ) of the insecticide dimethoate in the Neotropical solitary bee Centris analis, a cavity-nesting oil-collecting bee distributed from Brazil to Mexico. Males and females of C. analis were exposed orally to dimethoate for 48 hours under laboratory conditions. The lethality was assessed every 24 hours until 144 hours after the beginning of the test. After the LD 50 calculation, we compared the value with available LD 50 in the literature of other bee species using the species sensitivity distribution curve. In 48 hours of exposure, the males showed an LD 50 value 1.33 times lower than females (32.78 and 43.84 ng a.i./bee, respectively). C. analis was more sensitive to dimethoate than the model species A. mellifera and the solitary bee from temperate zones, Osmia lignaria. However, on a body weight basis, C. analis and A. mellifera had similar LD 50 values. This is the first study that calculated an LD 50 for a Neotropical solitary bee. Besides, the results presented here are of crucial importance for a better understanding of the effects of pesticides on the tropical bee fauna and will help to improve the risk assessment of pesticides to bees under tropical conditions, giving attention to wild species, which is commonly neglected.