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The stingless bee Melipona capixaba Moure and Camargo, 1994 is endemic to the Brazilian Atlantic Forest. Its occurrence is restricted to highlands in the Espírito Santo State, and it has possibly the smallest known geographic distribution among the cataloged stingless bees. It is therefore considered to be an endangered species. Perhaps because of its small area of occurrence, or because it was only identified two decades ago, little is known about the biology of this species, its current geographic distribution, or its actual preservation status. Here, we present the results from the largest sampling of M. capixaba conducted in its natural habitat. We developed a distribution map by using a geographic information system. Our data indicate that M. capixaba is found in the municipalities of Espírito Santo State at altitudes between 800 m and 1,200 m; with annual average temperatures around 18–23°C; precipitation more than 1,200 mm per year; and vegetation cover-type Mountain Dense Ombrophylous Forest, restricted to an area of approximately 3,450 km2. We observed colonies both in their natural habitat and under conditions of ex situ maintenance, and identified the key challenges and prospects for the conservation of this endangered bee.

Declines in pollinator colonies represent a worldwide concern. The widespread use of agricultural pesticides is recognized as a potential cause of these declines. Previous studies have examined the effects of neonicotinoid insecticides such as imidacloprid on pollinator colonies, but these investigations have mainly focused on adult honey bees. Native stingless bees (Hymenoptera: Apidae: Meliponinae) are key pollinators in neotropical areas and are threatened with extinction due to deforestation and pesticide use. Few studies have directly investigated the effects of pesticides on these pollinators. Furthermore, the existing impact studies did not address the issue of larval ingestion of contaminated pollen and nectar, which could potentially have dire consequences for the colony. Here, we assessed the effects of imidacloprid ingestion by stingless bee larvae on their survival, development, neuromorphology and adult walking behavior. Increasing doses of imidacloprid were added to the diet provided to individual worker larvae of the stingless bee Melipona quadrifasciata anthidioides throughout their development. Survival rates above 50% were only observed at insecticide doses lower than 0.0056 µg active ingredient (a.i.)/bee. No sublethal effect on body mass or developmental time was observed in the surviving insects, but the pesticide treatment negatively affected the development of mushroom bodies in the brain and impaired the walking behavior of newly emerged adult workers. Therefore, stingless bee larvae are particularly susceptible to imidacloprid, as it caused both high mortality and sublethal effects that impaired brain development and compromised mobility at the young adult stage. These findings demonstrate the lethal effects of imidacloprid on native stingless bees and provide evidence of novel serious sublethal effects that may compromise colony survival. The ecological and economic importance of neotropical stingless bees as pollinators, their susceptibility to insecticides and the vulnerability of their larvae to insecticide exposure emphasize the importance of studying these species.