The commercial insecticide Fastac Duo is a combined insecticide, widely used in different crops, acting on insects, affecting both pests and pollinators, such as bees. In this study, the effects of sublethal concentrations of Fastac Duo in stingless bees Scaptotrigona bipunctata were evaluated. Worker forager bees were exposed to the insecticide and histochemical and morphological analyses were conducted after 24, 48 and 72 h of ingestion. Brain analysis of S. bipunctata revealed changes in the chromatin condensing state according to exposure time and insecticide concentration when compared to the control group. Morphological changes were observed in the midgut in all concentrations and exposure times, which may interfere in several physiological processes. In conclusion, although the concentrations used in the study did not cause high mortality, it induced changes in the internal morphology that can lead to changes in bee activity.

The meliponines can be found in tropical and subtropical regions and is observed in the majority of Latin America. Scaptotrigona bipunctata are stingless bees that build colonies that possess between 2,000 and 50,000 individuals. This study aimed to estimate the toxicity of the insecticide acephate after oral and contact contamination in S. bipunctata. Results revealed differences between the two types of contamination and indicated that S. bipunctata is tolerant to acephate since the mortality rate was low. The findings indicated that there were expression changes of isoenzyme esterases after contamination with the insecticide, which was able to partially inhibit almost all of the enzymes identified in this study. In addition, morphological changes were identified in the midgut of the bees in the first 24 hours of contamination. However, after 48 hours it was observed the regeneration of the peritrophic membrane and other structures, contributing to the survival of the insects. It is essential to propose measures to minimize the impact of agrochemicals on pollinators and this study provides support for investigations on pesticide toxicity in stingless bees.

Agrochemicals are considered one of the factors responsible for the decline of bee population in the world, causing a huge amount of losses. The organism of these insects seeks an alternative for their survival and adaptive factors can be triggered, such as the action of antioxidant substances, which can promote protection via the digestive system. This study aimed to evaluate the enzymatic activity and total antioxidant capacity in the midgut of adult Apis mellifera workers that had been selected since 2015 to be tolerant to the neonicotinoid insecticide thiamethoxam. For this, tolerant and non-tolerant honeybees were contaminated with thiamethoxam for 24 hours. Then the midgut was dissected for the enzymatic analysis. The results obtained showed that tolerant bees presented a significant result regarding the enzymatic activity and total antioxidant capacity for the reduction of damage caused by thiamethoxam when compared to the non-tolerant group.

Interaction between bees and plants ensured success in cross-pollination crops, increasing the vigor of the species, as the production of fruits and seeds. Bees are the main pollinators of angiosperms and several crops. Among the factors related to the disappearance of bees in agricultural areas is the excessive or improper use of insecticides. However, agriculture is extremely dependent on pesticides for pest control and the neonicotinoid thiamethoxam is one of the most used insecticides. The use of these chemicals affects the pollinating bee Apis mellifera. Thus, the aim of the study was to select Africanized A. mellifera queens tolerant to thiamethoxam, producing four generations of bees kept in chronic contamination and perform tests to validate tolerance. Colonies of A. mellifera were subjected to chronic contamination by contact with thiamethoxam at a sublethal concentration of 1.65 mg a.i./L. From the surviving colonies, four generations of new queens were produced, kept in chronic contamination with thiamethoxam. Chronic contamination caused changes in the workers' behavior for 25 days. Validation of selection and tolerance was performed in vitro bioassays to verify mortality and critical electrolyte concentration (CEC). In vitro bioassays showed that there was low mortality after contamination for 24 hours by contact with thiamethoxam at 82.5 mg a.i / L. The analyzes of CEC indicate that there was an increase in gene expression in brain cells, probably as an attempt to detoxify the workers' organism by contamination with thiamethoxam. New tests need to be carried out with colonies tolerant to the neonicotinoid thiamethoxam, but these initial results indicate that these queens have potential to tolerate this neonicotinoid.