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cuckoo bee, any of more than 3,000 species of solitary bees that engage in brood parasitism, a form of kleptoparasitism in which the bees deposit their eggs in the food-provisioned nests of other bees. Cuckoo bees are found on every continent except Antarctica and occupy a range of habitats. The term cuckoo bee is a behavioral descriptor and not a taxonomic group. As such, bees that exhibit this behavior are found in a number of families and genera, including cloak-and-dagger bees (Thyreus, family Apidae), sharptail bees (Coelioxys, family Megachilidae), Triepeolus and Epeolus (both in the family Apidae), blood bees (Sphecodes, family Halictidae), Stelis (family Megachilidae), and nomad bees (Nomada, family Apidae), the largest group of cuckoo bee species. There are even several species of cuckoo bumblebees (Bombus, family Apidae).

Physical description

A large non-taxonomic group, cuckoo bees are diverse in appearance. As insects, they have a body formed of a head, a thorax, and an abdomen and have a set of six legs. Like other bees, they have a pair of large compound eyes on the sides of the head and three ocelli (simple eyes) on the top of the head. Many species have distinctive thick antennae. Some cuckoo bee larvae have large or specialized mandibles to effectively kill other bee larvae.

Cuckoo bees are generally thicker and more compact than other solitary bee taxa, and many have smooth, almost hairless bodies. Some are mistaken for wasps. Given that cuckoo bees do not need to collect pollen for their offspring, their legs lack the corbiculae, or pollen baskets, common among bumblebees and honeybees. The bees range widely in coloration, and a number of species are iridescent. Some cuckoo bees may have evolved to visually mimic their host species.

Natural history

Did You Know?

Epeolus attenboroughi is a species of cuckoo bee named for David Attenborough. The bee is one of many organisms named for the beloved English naturalist.

Like most bees, cuckoo bees are solitary, meaning that they do not dwell in social hive communities. They are called cuckoo bees because they lay their eggs in the nests of other bees in a manner analogous to some cuckoo birds (order Cuculiformes), which lay eggs in the nests of other birds. Most cuckoo bees infiltrate the nests of solitary bees, though cuckoo bumblebees exploit bumblebee colonies to raise their young. Some cuckoo bees target a single species of bee host, while others are generalists and can parasitize several host species.

The female cuckoo bee infiltrates the nest of another bee and deposits an egg in a cell designed for the other bee’s offspring. Some species destroy the host egg and replace it with their own. In others, the cuckoo bee larva either kills the other egg or larva directly (and sometimes eats it) or starves it to death by devouring all the food provisioned in the cell. After consuming the food, the cuckoo bee larva pupates and emerges from the nest as an adult. Cuckoo bees often mate in the summer, though they may reproduce year-round in tropical and semitropical climates.

Threats and conservation

Anthropogenic environmental degradation, including global warming, pesticide use, and land-use changes, presents risks to cuckoo bee populations. In addition to their own needs for sufficient habitat and nectar sources, as obligate parasites, cuckoo bees are also affected by declines in their host species.

Anna Dubey
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Top Questions

What is a bee?

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Experts baffled by mass bee deaths Mar. 29, 2025, 3:08 AM ET (CBS)

bee, (superfamily Apoidea), any of more than 20,000 species of insects in the suborder Apocrita (order Hymenoptera), including the familiar honeybee (Apis) and bumblebee (Bombus) as well as thousands more wasplike and flylike bees. Adults range in size from about 2 mm to 4 cm (about 0.08–1.6 inches).

Bees are closely related to certain types of wasps, the principal biological difference between them being that bees (except for parasitic cuckoo bees) provide their young with pollen and sometimes honey, whereas wasps feed their young animal food or provision their nests with insects or spiders. Associated with this difference in food preference are certain structural differences, the most essential being that wasps are covered with unbranched hairs, whereas bees have at least a few branched or feathered hairs to which pollen often clings.

Bees are entirely dependent on flowers for food, which consists of pollen and nectar, the latter sometimes modified and stored as honey. There is no doubt that bees and the flowers that they pollinate evolved simultaneously. As bees go from flower to flower gathering pollen, a small amount is rubbed from their bodies and deposited on the flowers they visit. This loss of pollen is significant, for it often results in cross-pollination of plants. The practical value of bees as pollinators is enormously greater than the value of the honey and wax of honeybees and stingless bees.

Dromedary camels (Camelus dromedarius). Animals, mammals.
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Male bees are usually short-lived and never collect pollen, nor do they have other responsibilities in connection with providing for the young. Female bees do all the work of nest making and provisioning and usually have special anatomical structures that assist them in carrying pollen. Most bees are polylectic, meaning that they gather pollen from a wide variety of flowers. However, some bees collect pollen only from flowers of certain families, others from flowers of certain colors. Oligolectic bees gather pollen from only a few related kinds of flowers. The mouth parts of bees, like the pollen-collecting and pollen-carrying devices, seem to be adapted to different flowers.

Most bees are solitary, or nonsocial, in habit and do not live in colonies. In these species each female makes her own nest (usually a burrow in the ground) and provisions it. Among such bees there are no castes. Some solitary bees make chimneys or turrets at the nest entrance, others nest in wood or in the pith of twigs or canes. Most solitary bees are short-lived as adults. Some species may be in flight only a few weeks of the year, having spent the rest of the year in their cells as eggs, larvae, pupae, and young adults.

Solitary bees provide all of the food the larvae require to complete development when the cells are sealed. Social bees, such as the bumblebee and the honeybee, feed their young progressively. For the life cycle of social bees, see bumblebee; honeybee; stingless bee.

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The Apoidea includes seven families: Colletidae, which are plasterer bees consisting of five or six subfamilies, about 45 genera, and some 2,500 species; Andrenidae, which are medium- and large-sized solitary mining bees, including some parasitic species; Halictidae, about 4,500 species of sweat bees, which are attracted to perspiration; Melittidae, bees that mark a transitional form between the lower and the higher bees; Megachilidae (leaf-cutting and mason bees), noted for their elaborate nest structures; Stenotritidae, a small family of Australian bees; and Apidae with some 5,700 species of bumblebees, honeybees, stingless bees, carpenter bees, and digger bees.

The Editors of Encyclopaedia BritannicaThis article was most recently revised and updated by Encyclopaedia Britannica.
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