Stingless bees are important pollinators and a highly diverse group of neotropical bees. In Brazil, for example, many species coexist in the same environment. But not everything is smooth sailing. Some stingless bee species live in silent warfare, involving hive invasions and food stealing. Let’s explore an intriguing group of bees: the Lestrimelitta, also known as robber bees.
Author: Ana Paula Cipriano
Leia em Português
The cleptoparasitic bees usually initiate their work with a few foragers attempting to locate a potential nest to attack. During this process, they identify a target and begin recruiting their nestmates to assist in a successful attack. An important chemical helping the robber bees in guiding their nestmates is citral, likely functioning as a pheromone with a recruitment role in these bees. This pheromone smells like lime, which is why these bees are popularly known as ‘abelhas limão’ (lime bees). Citral may also serve another crucial function in the attack process by acting as a barrier to workers from the nest under attack. These workers may react to the citral and avoid entering their own nest for a while, instead staying close to the entrance and hovering.
The attacks can last from hours to weeks, with the main goal of collecting as much resources from the robbed hive as possible. Interestingly, the same hive can be attacked many times, which suggests a memorized process from the robber bees. On the other hand, the hosts may also learn how to protect themselves against these raids, focusing on saving their workers and resources. For example, Plebeia (abelha mirim) or Nannotrigona (abelha irai) workers may tolerate the attacks and instead of fighting with the robber bees, they can try to save some of the hive resources by drinking the liquid food and hiding until the end of the attack. In this context, different species have defence strategies that include resin deposition, guard behaviour and camouflaged nests.
One great way of dealing with robber bees and other predators is to avoid the attack. In natural environments, some stingless bees can build their nests on the ground and with tiny and discrete entrances, which make them less perceptive to other animals. Additionally, Jatai bees, for example, have specialised guards, the soldiers, that are larger compared to workers and stay close to the entrance tube, always ready to call more guards if they need to face an enemy. Lastly, some Melipona bees, such as Melipona seminigra (uruçu-boca-de-renda), protect their nests by adding balls of mud and blocking the entrance during nest invasions.
Defensive strategies against robber bees can be diverse, representing the amazing species diversity of stingless bees. This silent warfare is a complex behaviour that has been acting as a changing force across stingless bee species, similar to a race in which cleptoparasites and host bees develop strategies to maintain their resources and guarantee the survival of their colonies.
In human-modified environments, such as meliponaries, the rules of this game can be different since the density of hives is much higher than in the natural environment. As citizens and scientists, we have the important role of understanding our impacts on natural resources and how these behavioural traits are changing. Due to their massive diversity, we still have much to learn from stingless bees, with the ultimate goal of protecting their existence and their crucial ecological services: the pollination of our biomes.
Bibliography
Grüter, C., 2020. Stingless bees: their behaviour, ecology and evolution. Springer Nature.
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