Barbut’s Cuckoo Bumblebee

Barbut’s cuckoo bumblebee (Bombus barbutellus) is a species of parasitic bumblebee that lives in Europe. Cuckoo bumblebees do not build nests, do not have queens, and do not produce honey. They share the name cuckoo with birds in the Cuculidae family. This is because of the cuckoo bird’s habit of laying their eggs in other birds’ nests. Cuckoo bumblebees deposit their eggs in the nests of other bees. Neither the birds nor the bees return to raise their young. Keep reading to learn how Barbut’s cuckoo bee larvae survive without a mother.

Five Facts about Barbut’s Cuckoo Bumblebee

• Barbut’s cuckoo bumblebee is named after James Barbut, an English painter and naturalist.
• Barbut’s cuckoo bumblebees live in Europe
• Barbut’s cuckoo bumblebees are parasites
• They are not good pollinators
• Barbut’s generally usurp the nests of Bombus ruderatus, the large garden bumblebee and Bombus hortorum the small garden bumblebee

Scientific Name

Bombus barbutellus, the scientific name for Barbut’s cuckoo bumblebee loosely translates to buzzing (Bombus) beard (barbutellus). However, barbutellus in this case is a reference to James Barbut (1711-1788), an English painter and naturalist. Barbut published a book in 1783 that contained detailed drawings of animals from Linnaeus’s Intestina and Mollusca. The father of modern taxonomy, Carl Linnaeus (1707-1778),is the person responsible for creating the vocabulary, or nomenclature, that is used in classifying animals. It is possible that Barbut and Linnaeus crossed paths or were acquainted. However, because Barbut was English and Linnaeus Swedish, it is unlikely.

Appearance

Barbut’s cuckoo bumblebees have black heads, light yellow and black striped bodies, and light yellow-to-cream colored tails. Cuckoo bumblebees typically plunder the nests of bumblebees that are similar in appearance. Barbut’s tend to seize the nests of Bombus hortorum and Bombus ruderatus, the small garden bumblebee in the large garden bumblebee, respectively. Though similarly colored, the host species have longer heads and longer tongues than the cuckoos, which have rounder heads that are the same width as their abdomen.

Cuckoos have no pollen baskets, called corbiculae (singularly, corbicula), and are not good pollinators. They have wax glands, but they are vestigial, meaning that they do not possess the ability to secrete wax. Thus, cuckoo bumblebees are unable to construct honeycomb. They are also slightly less hairy than ordinary bumblebees. Cuckoos have much harder exoskeletons than regular bumblebees, which serve them well in their conquests of the host queens. Regarding their sizes, Barbut’s cuckoo is the mid-size version, measuring in between Bombus ruderatus and Bombus hortorum. Naturally occurring variations of size and coloration aid the cuckoo bumblebee’s to infiltrate host nests.

Behavior

Barbut’s cuckoo bumblebees are typically solitary creatures who spend their lives foraging for nectar and pollen. Cuckoo bumblebees do not live in colonies. Evolutionary adaptions have resulted in their inability to construct nests or produce honeycomb. Both of these are required components of a healthy colony. Absent the ability to establish their own colonies, cuckoo bumblebees must rely on other species of bumblebees to provide for their young. In late spring when she is ready to lay her eggs, the female cuckoo bumblebee will attack the host’s nest killing the queen. She then buzzes around in the nest long enough to appropriate the nest’s scent. This ensures that the host colony accepts her offspring as its own.
Once the cuckoo has laid her eggs she departs the nest, never to return. The rest of her days are spent foraging for nectar and pollen which give her energy. While forging, cuckoo bumblebees will sometimes accidentally pollinate a few flowers. However, evolutionary adaptations have rendered them incapable of being effective pollinators.

While the cuckoo bumblebees are out foraging, their progeny are wreaking havoc back at the host nest. Cuckoo bumblebees hatch earlier than host species. They consume the resources that were meant to nourish the host larvae. cuckoo larvae sometimes even eat the host larvae. When their numbers are large cuckoo bumblebee larvae decimate entire host colonies.

Habitat

Barbut’s bumblebees live throughout Europe. They live along the coasts of England and are especially prevalent in the Southern U.K. Barbut’s bumblebees forage in grasslands, meadows, and heaths. They are also visible in gardens and other urban or suburban green spaces. Because they do not construct nests or live in colonies, cuckoo bumblebees tend to live in areas that are rich in variety and quantity of flowering plants.

Diet

Barbut’s bumblebees are generalist foragers, feeding on whatever flowering plants are available in their environment. They feed on the nectar and pollen of flowering plants like thistle, lavender, and honeysuckle. The nectar provides them with energy, while the pollen supplies the various nutrients and proteins necessary to maintain their bodies. Like ordinary bumblebees, cuckoos extract nectar from flowers using their tongues. Because they don’t live in colonies, their focus is on foraging for themselves.

Predators

A variety of animals prey on Barbut’s cuckoo bumblebees. Birds, bats, spiders, and other insects are among their predators. Many species of birds will eat bumblebees and their larvae. The European bee-eater, (Merops apiaster), consumes up to 250 bees daily! Before eating the bees, Merops apiaster removes the bee’s stinger by repeatedly striking it against a hard surface until the stinger falls off. Cross orb-weavers (Araneus diadematus), flower crab spiders (family Thomasidae), and other garden spiders will eat bumblebees that fly into their webs. Insects prey on cuckoo bumblebees, too. Cuckoo wasps are among them.

Threats

Climate change, pesticide use, and habitat loss are threats to Barbut’s cuckoo bumblebees. These factors reduce foraging areas, which in turn reduce suitable habitats, resulting in few host nests for the cuckoo bumblebees to infiltrate. Competition from and parasitism by other cuckoo bee species are additional threats to the species. Barbut’s bumblebees are a beneficial species that control populations of other species of bees. Host species that are unrestrained can increase quickly, resulting in overpopulation and competition for food. In areas with limited resources, non-honey-producing species deplete the food supply, leaving honey bees to suffer. Colony collapse results when resources are too restricted.

Conservation Status / Population

The IUCN Red List of Threatened Species classifies Bombus barbutellus as a species of least concern. Cuckoo bumblebee populations are consistently in flux. Mast years when their numbers are relatively stable may be followed by a decade of decline. However, indications point to an overall decline in the Bombas genus, and the family Apidae. The decline is rapid and tied to climate change in habitat loss. Population estimates for specific species of cuckoo bumblebees are not determined. Cuckoo bumblebees are not well-researched and because they do not construct nests or live in colonies, they are difficult to track.

Lifecycle

The lifecycle of Barbut’s cuckoo bumblebee is simple, direct, straightforward, and repetitive. In late spring to early summer female cuckoo bumblebees will begin the search for host nests in which to lay their eggs. It is thought that they use scent to find appropriate nests. Once a nest has been selected, the cuckoo bumblebee will attack the nest. She must make her way past numerous worker bees before attacking and killing the queen. Once the queen is dead, the cuckoo bumblebee will attempt to become an accepted member of the colony before laying her eggs. Having laid her eggs, the cuckoo bumblebee retreats from the nest and will not return. She spends the rest of her life foraging.

The larvae of Barbut’s cuckoo bumblebee hatch a day or two prior to the host colony’s larva. The cuckoo larvae consume the resources intended for the host larvae, sometimes even consuming the host larvae. Once they reach maturity the females of the species resume the cycle. Because cuckoo bumblebees lay parthenogenetic eggs that do not require fertilization, not much is known about male cuckoo bumblebees.

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