-At present, numbers of both wild and managed bee colonies are declining rapidly, causing global concern for pollination services. Stingless bees play an important ecological role as pollinators of many wild plant species and seem good candidates for future alternatives in commercial pollination. This paper reviews the effectiveness of stingless bees as crop pollinators. Over the past six years the number of crops reported to be effectively pollinated by stingless bees has doubled, putting the total figure on 18 crops. Eleven stingless bee species across six genera have been found to forage effectively under enclosed conditions, indicating the potential of stingless bees as pollinators of greenhouse crops. The biological features that make stingless bees strong candidates for commercial pollination services are discussed, together with their present limitations. The effects of natural vegetation and wild bees on crop yield are reviewed, and make a strong case for habitat conservation.agriculture / alternative pollinators / food crop / greenhouse / Meliponini

Novice foragers of social bees have to decide what food commodity to collect when they start foraging for the first time. In this decision making process two types of factors are involved: internal factors (the response threshold) and external factors (environmental and colony conditions). In this study we will focus on the importance of two external factors, pollen storage level and information from experienced foragers about food availability in the field, on the initial commodity choice of foragers of the stingless bee species Plebeia tobagoensis. We also studied the effect of the initial choice of individuals on their subsequent foraging career. This study was performed in a closed greenhouse compartment, where food availability and colony condition could be controlled.Information on food availability in the field from experienced foragers and pollen storage level both greatly influenced the initial commodity choice of individuals, with more choices for the commodity communicated by experienced foragers or lacking in storage. The initial choice of foragers is of importance for their future foraging career, although a substantial proportion of foragers did switch between food commodities. Because of the ability of novice foragers to become flexibly distributed over foraging tasks, social bees are able to react to changes in their environment without directly having to decrease foraging effort devoted to other foraging tasks. This, in combination with individual flexibility during foraging careers makes it possible for colonies of P. tobagoensis to forage efficiently in an ever-changing environment.

-The deposition and use of scent marks on food sources has been found in foraging solitary bees, bumblebees, stingless bees and honeybees. The widespread existence of this communication mechanism points to its ecological significance. The importance of the depositor's identity on the use of food source scent marks, however, has never been systematically investigated in the same bee species. Here we present strong evidence that individual foragers of the stingless bee species Trigona corvina scent marked a high quality food source and that they used their own scent marks to relocate it in choice experiments. T. corvina foragers showed a similar significant preference for a food source scent marked by their nest mates and by bees from a conspecific colony over a non-scent marked food source. However, no evidence for the use of scent marks deposited by other stingless bee species was found. The implications of these findings for the evolution of food source scent marking in bees are discussed. scent mark / food source / depositor / stingless bee / Trigona / chemical communication

-This study reports on the occurrence and dynamics of foraging task specialisation in the stingless bee Plebeia tobagoensis. We test the hypothesis that in a stable environment foraging task specialisation is preferred, but that individuals readily switch to other foraging tasks when changes in food availability occur. The study was performed in a greenhouse, where food availability could be controlled. When all food sources were available, most individuals (71%) specialised on the collection of one food commodity. When this commodity was removed 50% of the specialists switched foraging tasks. When comparing foraging performance of flexible and specialised foragers we found that specialised bees performed better. However, most specialised foragers do make a costly switch to other foraging tasks when a change in food availability occurs. It seems likely that this high individual flexibility is adaptive for relatively small social bee colonies, living in a dynamic environment. task specialisation / foraging performance / food availability / stingless bees / Plebeia

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