Bees are insects belonging to the clade Anthophila, part of the superfamily Apoidea, which also includes various wasps. Unlike their carnivorous or omnivorous relatives, all bees are herbivores, relying exclusively on pollen for protein and nectar for carbohydrates to feed their developing young. This commitment to floral resources has led to immense diversification. Scientists currently recognize over 20,000 known bee species worldwide.
The Approximate Global Count
This diversity places bees among the most numerous groups of insects, far outnumbering the combined species count of all birds and mammals. Scientists classify this biodiversity into seven recognized families. These include Apidae (honeybees and bumblebees) and Megachilidae (often cavity-nesting species). Halictidae (sweat bees) and Andrenidae (mining bees) are two other large and widespread families. The remaining families—Colletidae, Melittidae, and Stenotritidae—contain less numerous but specialized bees. The Western honeybee, Apis mellifera, widely managed for agriculture, represents only a tiny fraction of this global diversity. Statistical models suggest the true species richness may be higher, potentially exceeding 24,700 species.
The Primary Division: Solitary Versus Social Bees
The primary distinction in bee lifestyles is the division between solitary and social species, separating the vast majority from the few well-known species. Approximately 90% of all bee species are solitary, meaning each female operates independently to build and provision her own nest. A solitary female excavates a nest, creates individual cells, deposits a pollen and nectar mass, lays a single egg, and then seals the cell. This lifestyle is characterized by the absence of a worker caste, cooperative brood care, or overlapping generations of adults.
Examples of this independent life include Leafcutter bees (Megachile spp.), which use pieces of leaves to line their brood cells, and Mason bees (Osmia spp.), which use mud and chewed plant material for cell construction. Once the female has provisioned all her cells, her maternal duties are complete, and she does not interact with the resulting offspring.
In sharp contrast, social bees, which include honeybees and bumblebees, exhibit a complex organization known as eusociality. This advanced social structure involves a reproductive division of labor, where a single queen is responsible for reproduction while non-reproductive female workers perform colony maintenance, foraging, and defense. Social colonies feature cooperative care of the young and the coexistence of multiple generations within the nest, creating a perennial or annual structure. The workers’ roles change as they age, progressing from hive maintenance and nursing duties to the task of foraging for pollen and nectar outside the nest.
Specialized Roles and Unique Appearances
Beyond the broad solitary and social classifications, bee species exhibit physical and behavioral specializations that allow them to exploit specific ecological niches. Metallic Sweat Bees (family Halictidae) often display iridescent coloration of metallic green, blue, or gold. These bees are attracted to human perspiration to collect salts, which earned them their common name.
Other species have evolved unique foraging adaptations, such as Oil-Collecting Bees in genera like Macropis and Centris, which gather floral oils instead of or in addition to nectar. These females possess specialized hairs on their legs to absorb oil from flower glands called elaiophores. The collected oil feeds their larvae or lines subterranean brood cells, providing a waterproof barrier. In African species of the genus Rediviva, females have evolved elongated forelegs to reach oil reserves deep within flower spurs.
A final group, the Cuckoo Bees, are kleptoparasites that infiltrate the nests of other bees to lay their eggs. Lacking the need to collect pollen, these bees often appear less fuzzy and more wasp-like, sometimes bearing warning colors of red, black, or yellow. The cuckoo bee larva consumes the host’s stored pollen and nectar provision, often after killing the host egg or young larva.