Stingless bee
Stingless bees, sometimes called stingless honey bees or simply meliponines, are a large group of bees, comprising the tribe Meliponini. They belong in the family Apidae, and are closely related to common honey bees, orchid bees, and bumblebees. These four bee tribes belong to the corbiculate bees' monophyletic group. Meliponines have stingers, but they are highly reduced and cannot be used for defense, though these bees exhibit other defensive behaviors and mechanisms. Meliponines are not the only type of bee incapable of stinging: all male bees and many female bees of several other families, such as Andrenidae and Megachilidae, also cannot sting.
Some stingless bees have strong mandibles and can inflict painful bites. Some species can present large mandibular glands for the secretion of caustic defense substances, secrete unpleasant smells or use sticky materials to immobilise enemies.
The main honey-producing bees of this group generally belong to the genera Scaptotrigona, Tetragonisca, Melipona and Austroplebeia, although there are other genera containing species that produce some usable honey. They are farmed in meliponiculture in the same way that European honey bees are cultivated in apiculture.
Throughout Mesoamerica, the Mayans have engaged in extensive meliponiculture on a large scale since before the arrival of Columbus. Meliponiculture was popular in Maya society, influencing their social, economic, and religious activities. The practice of maintaining stingless bees in man-made structures is prevalent across the Americas, with notable instances in countries such as Brazil, Peru, and Mexico.
Taxonomy
The taxon Meliponini was first erected by the German entomologist Karl Hermann Konrad Burmeister in 1876. It is currently classified as a tribe within the family Apidae, which also includes honey bees, bumble bees, and orchid bees. The name Meliponini is derived from the genus Melipona, which is a major genus within the tribe. The term melipona comes from the Greek words meli, meaning "honey", and pōnē, meaning "labor" or "toil", referencing their role as honey producers. Members of Meliponini are commonly known as stingless bees due to their highly reduced stingers, which are non-functional for defense. Despite this, they are capable of biting and exhibit complex colony defense strategies.Geographical distribution
Stingless bees can be found in most tropical or subtropical regions of the world, such as the African continent, Southeast Asia and Australia, and tropical America.The majority of native eusocial bees of Central and South America are SB, although only a few of them produce honey on a scale such that they are farmed by humans. The Neotropics, with approximately 426 species, boast the highest abundance and species richness, ranging from Cuba and Mexico in the north to Argentina in the south.
They are also quite diverse in Africa, including Madagascar, and are farmed there also. Around 36 species exist on the continent. The equatorial regions harbor the greatest diversity, with the Sahara Desert acting as a natural barrier to the north. The range extends southward to South Africa and southern Madagascar, with most African species inhabiting tropical forests or both tropical forests and savannahs.
Meliponine honey is prized as a medicine in many African communities, as well as in South America. Some cultures use SB honey against digestive, respiratory, ocular and reproductive problems, although more research is needed to disclose evidence that supports these practices.
In Asia and Australia, approximately 90 species of stingless bees span from India in the west to the Solomon Islands in the east, and from Nepal, China, and Taiwan in the north to Australia in the south.
Origin and dispersion
Phylogenetic analyses reveal three distinct groups in the evolutionary history of Meliponini: the Afrotropical, the Indo-Malay/Australasia, and the Neotropical lineages. The evolutionary origin of the Meliponini is Neotropical. Studies observing contemporary species richness show that it remains highest in the Neotropics.The hypothesis proposes the potential dispersion of stingless bees from what is now North America. According to this scenario, these bees would have then traveled to Asia by crossing the Bering Strait and reached Europe through Greenland.
Evolution and phylogeny
Meliponines form a clade within the corbiculate bees, characterized by unique pollen-carrying structures known as corbiculae located on their hind legs. This group also includes another three tribes: honey bees, bumble bees, and orchid bees. The concept of higher eusociality, defined by the presence of distinct queen and worker castes and characterized by features such as perennial colony lifestyles and extensive food sharing among adults, is particularly relevant in understanding the social structure of these tribes. Both Meliponini and Apini tribes are considered higher eusocial, while Bombini is considered to be primitively eusocial.The phylogenetic relationships among the four tribes of corbiculate bees have been a topic of considerable debate within the scientific community. Two primary questions arise: the relationship of stingless bees to honey bees and bumble bees, and whether their eusocial behavior evolved independently or from a common ancestor. Morphological and behavioral studies have suggested that Meliponini and Apini are sister groups, indicating a single origin of higher eusociality. In contrast, molecular studies often support a relationship between Meliponini and Bombini, proposing independent origins of higher eusociality in both Apini and Meliponini.
A morphological, behavioral, and molecular data analysis provided strong support for the latter hypothesis of dual origins of higher eusociality. Subsequent research has reinforced the idea that stingless bees and honey bees evolved their eusocial lifestyles independently, resulting in distinct adaptive strategies for colony reproduction, brood rearing, foraging communication, and colony defense. This divergence helps explain the varied ecological and social solutions developed by these two groups of bees, such as foraging communication, colony defense/reproduction and brood rearing.
Fossil history
The fossil record for stingless bees is notably robust compared to that of many other bee groups, with twelve extinct species currently identified. Fossils of these bees are primarily found in amber and copal, where excellent preservation typically occurs. This favorable fossilization process may be attributed to the behaviors of stingless bees, which collect tree resin for nest building and defense, increasing the likelihood of entrapment.Despite this relatively good fossil record, the evolutionary history of stingless bees remains poorly understood, particularly regarding their widespread distribution across various ecological niches around the globe. The oldest known fossil stingless bee is Cretotrigona prisca, a small worker bee approximately 5 mm in body length, discovered in New Jersey amber. This species is believed to have existed during the Late Cretaceous period, around 65–70 million years ago, marking it as the oldest confirmed fossil of an apid bee and the earliest fossil evidence of a eusocial bee. C. prisca exhibits striking similarities to extant stingless bees, indicating that the evolutionary lineage of meliponines may date back to this period.
Some researchers suggest that stingless bees likely evolved in the Late Cretaceous, approximately 70–87 million years ago. According to recent studies, corbiculate bees, which include stingless bees, are thought to have appeared around 84–87 million years ago, further supporting the notion of their evolution during this dynamic period in Earth's history.
Behaviour, biology and ecology
Overview
Meliponines, considered highly eusocial insects, exhibit a notable caste division. The colonies typically consist of a queen, workers, and sometimes male drones. The queen is responsible for reproduction, while the workers perform various tasks such as foraging, nursing, and defending the colony. Individuals work together with a well-defined division of labor for the overall benefit.Stingless bees are valuable pollinators and contribute to ecosystem health by producing essential products. These insects collect and store honey, pollen, resin, propolis, and cerumen. Honey serves as their primary carbohydrate source, while pollen provides essential proteins. Resin, propolis, and cerumen are used in nest construction and maintenance.
Nesting behavior varies among species and may involve hollow tree trunks, external hives, the soil, termite nest or even urban structures. This is linked to their resilience and ability to coexist with human activities.
Castes
Workers
In a SB colony, workers constitute the predominant segment of the population, serving as the colony's primary workforce. They undertake a multitude of responsibilities linked to the colony's well-being, including defense, cleaning, handling building materials, and the collection and processing of food. Recognizable by the corbicula—a distinctive structure on their hind legs resembling a small basket—workers efficiently carry pollen, resin, clay, and other materials gathered from the environment. Given their abundance and unique physical feature, workers play a central role in sustaining the colony.Queens
The principal egg layer in SB colonies is the queen, distinguished from the workers by differences in both size and shape. Stingless bee queens - except in the case of the Melipona genus, where queens and workers receive similar amounts of food and thus exhibit similar sizes - are generally larger and weigh more than workers. Post-mating, meliponine queens undergo physogastry, developing a distended abdomen. This physical transformation sets them apart from honey bee queens, and even Melipona queens can be easily identified by their enlarged abdomen after mating.Stingless bee colonies typically follow a monogynous structure, featuring a single egg-laying queen. An exception is noted in Melipona bicolor colonies, which are often polygynous. Depending on the species, queens can lay varying quantities of eggs daily, ranging from a dozen to several hundred. While information on queen lifespans is limited, available data suggest that queens generally outlive workers, with lifespans usually falling between 1 and 3 years, although some queens may live up to 7 years.
The laying queen assumes the role of producing eggs that give rise to all castes within the colony. Additionally, she plays a pivotal role in organizing the colony, overseeing a complex communication system primarily reliant on the use of pheromones.