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International audienceThe objective of this study was to evaluate the temperature sensitivity of three stingless bee species, one from the tropical highland transition Neartic-Neotropical region (Melipona colimana) and two from the tropical lowland regions (Melipona beecheii and Scaptotrigona hellwegeri) of Mexico. The changes in thoracic temperature, behavior, and mortality rate of workers and pupae of the three species submitted to control high and low temperatures were assessed. Workers of highland M. colimana regurgitated water and fanned their wings when submitted to high temperatures, a behavior reported here for the first time in a stingless bee. M. colimana consumed syrup and increased its thoracic temperature in response to cold environment. Workers and pupae of M. colimana experienced lower mortality rates than M. beecheii and S. hellwegeri. The results of this study showed the tolerance of M. colimana to a wider temperature range, possibly as a response to extreme conditions in its native environment. The implications of thermal susceptibility differences for the conservation of highland and lowland stingless bees are discussed

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The microsporidian parasite Nosema ceranae and neonicotinoid insecticides affect the health of honey bees (Apis mellifera). However, there is limited information about the effect of these stressors on other pollinators such as stingless bees (Hymenoptera: Meliponini). We examined the separate and combined effects of N. ceranae and the neonicotinoid thiamethoxam at field-exposure levels on the survivorship and cellular immunity (hemocyte concentration) of the stingless bee Melipona colimana. Newly-emerged bees were subjected to four treatments provided in sucrose syrup: N. ceranae spores, thiamethoxam, thiamethoxam and N. ceranae, and control (bees receiving only syrup). N. ceranae developed infections of > 467,000 spores/bee in the group treated with spores only. However, in the bees subjected to both stressors, infections were < 143,000 spores/bee, likely due to an inhibitory effect of thiamethoxam on the microsporidium. N. ceranae infections did not affect bee survivorship, but thiamethoxam plus N. ceranae significantly increased mortality. Hemocyte counts were significantly lower in N. ceranae infected-bees than in the other treatments. These results suggest that N. ceranae may infect, proliferate and cause cellular immunosuppression in stingless bees, that exposure to sublethal thiamethoxam concentrations is toxic to M. colimana when infected with N. ceranae, and that thiamethoxam restrains N. ceranae proliferation. These findings have implications on pollinators’ conservation.

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