A long-term study on the production of sexual offspring in relation to food stores was conducted in the stingless bee Melipona beecheii. Firstly, the production of sexuals was followed during one year in 10 colonies kept under natural conditions. Of the brood produced, 22.9 % were males, and of all female brood, 14.6 % were queens. Secondly, we measured the effect of experimentally manipulating the amount of food stores. One set of colonies started with 1.5 kg of food reserves and were regularly fed with pollen and nectar while another set were subjected to reduced food reserves of 0.5 kg, and were not given any extra food. Throughout the study, colonies with no treatment had brood and adults of both sexes all year round with no evidence of their presence being linked to swarming. Colonies with reduced food stores produced fewer males (0.7 %) and queens (10.5 %) than untreated colonies or colonies with enlarged food stores. The production of sexuals in colonies with enlarged food stores (23.4 % males, 13.5 % queens) did not differ significantly from that under natural conditions.We conclude that in Melipona only colonies that have accumulated large food stores produce sexuals that contribute to the reproductive population. This may lead to marked differences in the amount of sexuals produced by different colonies, although at the population level sexuals may be present all year round.

Summary Traditional tropical agriculture often entails a form of slash‐and‐burn land management that may adversely affect ecosystem services such as pollination, which are required for successful crop yields. The Yucatán Peninsula of Mexico has a >4000 year history of traditional slash‐and‐burn agriculture, termed ‘milpa’. Hot ‘Habanero’ chilli is a major pollinator‐dependent crop that nowadays is often grown in monoculture within the milpa system.We studied 37 local farmers’ chilli fields (sites) to evaluate the effects of landscape composition on bee communities. At 11 of these sites, we undertook experimental pollination treatments to quantify the pollination of chilli. We further explored the relationships between landscape composition, bee communities and pollination service provision to chilli.Bee species richness, particularly species of the family Apidae, was positively related to the amount of forest cover. Species diversity decreased with increasing proportion of crop land surrounding each sampling site. Sweat bees of the genus Lasioglossum were the most abundant bee taxon in chilli fields and, in contrast to other bee species, increased in abundance with the proportion of fallow land, gardens and pastures which are an integral part of the milpa system.There was an average pollination shortfall of 21% for chilli across all sites; yet the shortfall was unrelated to the proportion of land covered by crops. Rather, chilli pollination was positively related to the abundance of Lasioglossum bees, probably an important pollinator of chilli, as well indirectly to the proportion of fallow land, gardens and pastures that promote Lasioglossum abundance. Synthesis and applications. Current, low‐intensity traditional slash‐and‐burn (milpa) agriculture provides Lasioglossum spp. pollinators for successful chilli production; fallow land, gardens and pasture therefore need to be valued as important habitats for these and related ground‐nesting bee species. However, the negative impact of agriculture on total bee species diversity highlights how agricultural intensification is likely to reduce pollination services to crops, including chilli. Indeed, natural forest cover is vital in tropical Yucatán to maintain a rich assemblage of bee species and the provision of pollination services for diverse crops and wild flowers.

Although variation in body size has been recently reported in stingless bees (Meliponini), empirical evidence evaluating possible factors related to such variation is lacking, and thus it is not clear if it may have an adaptive significance. We evaluated if variation in the body size and weight of workers of stingless bees fluctuates across a seasonal pattern and if this could be related to characteristics of the food consumed during the larval stage. The weight of larval provisions, their protein, and sugar content were evaluated in four colonies of Nannotrigona perilampoides every 2 months across 1 year. Worker-destined larvae from the same combs were allowed to develop and were sampled as callow workers to determine their weight and size using morphometric data. The weight and size of workers were highly correlated and varied across the seasons in established colonies, suggesting that size variation cycles across the year in stingless bees. An increase in the protein content and, to a lesser degree, the quantity of larval food were positively linked to variation in body weight and size; food with richer protein content resulted in larger and heavier workers. This study provides the first evidence of an effect of the quantity and composition of larval food on the size of workers in stingless bees. Although body weight and size of workers differed across seasons, they were not readily noticeable as changes seem to occur as a continuum across the year. Since size polymorphism was of a larger magnitude across time but not within age cohorts and as it was highly determined by food resources, it may not be an adaptive feature in stingless bees. However, more studies are needed to determine the role of the cyclical change in worker body size on colony performance and thus its adaptive significance in stingless bees.

Importation of exotic bumblebees for greenhouse pollination may be restricted in México, thus making it necessary to evaluate the potential of native species as pollinators in enclosures. We studied the foraging activity and fruit production of tomato using one colony of Nannotrigona perilampoides (NP) and one colony of Bombus impatiens (BI) in greenhouses with ≈1000 plants. Mechanical vibration (MV) was included as a test treatment. The foraging activity was measured as the number of flowers visited within 5 min, the time spent on a flower collecting pollen, the number of visits that a flower received and the duration of a foraging trip. BI collected pollen more rapidly, visited more flowers within 5 min and did more visits per flower when compared with NP that also lasted longer in their trips. Significant correlations were found between environmental variables and the number of bees entering the hive and the number of bees on the flowers. For NP, the highest correlation was found for light intensity whilst in BI a negative effect of environmental temperature was detected. Regarding the quantity of fruit, BI resulted in higher fruit set when compared with NP, but the latter performed similarly to MV. However, the weight of the fruit and seed number was significantly higher for BI when compared with NP, and this was higher than for MV. Our results demonstrate that at the densities of tomato plants tested, one colony of BI was more efficient pollinator when compared with NP. We suggest that pollination efficiency of NP could have been limited by a reduced number of foragers on the plants at a given time and their limited flight range when compared with BI. Therefore, it will be necessary to evaluate if increasing densities of colonies of NP could improve tomato yield in tropical greenhouses.

Stingless bees are potential pollinators of commercial tropical crops and their use may increase in the short term. However, studies comparing the toxicity of pesticides to different individuals and species are lacking, making it difficult to evaluate their short- and long-term effects on colonies and populations of these insects. In this work, we tested the lethality of compounds from the main pesticide groups on stingless bees of the species Melipona beecheii Bennett, Trigona nigra Provancher, and Nannotrigona perilampoides Cresson. The LDo (in micrograms per bee) for each pesticide was calculated for callow workers and foragers of the three species as well as for gynes and drones of M. beecheii. The results showed that all species were highly susceptible to the evaluated compounds. Nicotinoid pesticides were the most toxic, followed in descending order by permethrin, diazinon, and methomyl. We found evidence of a relationship between the body weight of the species and their LD50 for permethrin and methomyl (r = 0.91 and 0.90, respectively) but not for diazinon (r = -0.089). An analysis of contingency tables showed that within each species, callow workers had higher mortalities than foragers (P < 0.01). In M. beecheii at similar pesticide dose more males died compared with females [chi2((0.0),1) = 10.16]. However, gynes were less resistant than workers [chi2((0.01),1)) = 8.11]. The potential negative consequences of pesticides to native stingless bees are discussed considering the reproductive biology of these insects. It is important to take actions to prevent damage to these key species for the ecology and agriculture of Mexico and Latin America