The world of bees extends far beyond the familiar image of the honey bee. Bees are insects within the order Hymenoptera, essentially wasps that have evolved to feed their young pollen and nectar instead of other insects. These small, often fuzzy, pollinators are fundamental to the reproduction of flowering plants across nearly every terrestrial ecosystem. The true diversity of this group encompasses an immense variety of sizes, shapes, and behaviors, far exceeding the large-colony life of the honey bee.
The Global Count: Why the Number Varies
The question of how many kinds of bees exist can only be answered with an estimate, as taxonomy—the science of classification—is a constantly evolving field. Scientists currently recognize more than 20,000 distinct species of bees worldwide, a figure exceeding the combined total of all bird and mammal species on Earth.
This number is not fixed and is subject to change due to several factors. New species are continually being discovered and formally described, especially in remote or under-studied regions. Taxonomic revisions, often based on genetic analysis, also play a role, leading to the splitting or merging of previously separate species.
Some statistical models suggest the true lower-bound for global bee species richness may be significantly higher, perhaps between 24,705 and 26,164 species. These higher estimates reflect the challenge of accurately surveying biodiversity, especially in areas like Asia and Africa. The accepted estimate of over 20,000 species remains the baseline, reflecting ongoing scientific exploration.
Defining Diversity: Solitary, Communal, and Social Lifestyles
The vast number of bee species can be grouped by their social organization, ranging from completely independent to highly complex colony structures. The overwhelming majority of the world’s bees, an estimated 90% of all species, live a solitary life. A solitary female constructs and provisions her own nest, often in a burrow in the ground or a tunnel in wood.
For solitary species, the mother collects a mass of pollen and nectar, lays a single egg upon it, seals the cell, and leaves the developing larva to fend for itself. She typically dies before the new generation emerges, meaning she never encounters her offspring. Examples include mason bees and mining bees, which work independently to ensure the survival of their young.
A less common arrangement is the communal lifestyle. Multiple females share a single, protected nest entrance but maintain separate, self-provisioned tunnels or cells inside. There is no cooperative care of the young or division of labor within the nest. Communal bees, such as some digger bees, gain safety by nesting in close aggregation, but each female remains responsible for her own brood.
The most well-known, but least common, social structure is eusociality, characterized by three traits: cooperative brood care, a reproductive division of labor, and overlapping adult generations. In a highly eusocial colony, like the European honey bee, a single queen is responsible for reproduction. Sterile female workers perform all other tasks, including foraging, nest defense, and tending to the young. Bumblebees exhibit primitively eusocial behavior, where the queen and workers are morphologically similar but maintain a clear division of labor.
The Six Major Bee Families
All known bee species are classified into major families, which provide a useful framework for understanding their shared evolutionary history and physical characteristics. While seven families are recognized globally, with the small Stenotritidae family being endemic to Australia, the six most widespread families account for the vast majority of global bee diversity.
The largest and most familiar family is Apidae. This diverse group includes the highly eusocial honey bees and bumblebees, as well as solitary species like carpenter bees and orchid bees. Apidae members exhibit the widest range of social behaviors, from solitary to advanced sociality.
The Megachilidae family includes leafcutter bees and mason bees, which are primarily solitary and build nests in pre-existing cavities. A distinguishing characteristic is that females carry pollen on a specialized patch of dense hairs located on the underside of their abdomen, rather than on their hind legs.
Halictidae, commonly known as sweat bees, is the second-largest family and includes species that are often metallic green or blue in color. These bees exhibit a wide range of sociality, from solitary to primitively eusocial, and many are ground-nesting.
The Andrenidae family, or mining bees, consists entirely of solitary, ground-nesting species active in the early spring. These bees typically dig burrows in the soil and are important pollinators for early-blooming plants.
Colletidae are often called plasterer bees or cellophane bees because the females line their nest cells with a unique, waterproof secretion produced from a gland in their abdomen. This family also includes the nearly hairless yellow-faced bees, which carry pollen internally in their crop.
The Melittidae family is a smaller group of specialized, mostly solitary bees that are not as widely distributed as the other families. Many species within this family collect floral oils, in addition to nectar and pollen, which they use to provision their young.