Field Cuckoo Bumblebee

Field cuckoo bumblebees (Bombus campestris) are common and widespread throughout Europe. These cuckoo bumblebees lay their eggs in the nests of other bumblebees. This is why they are called cuckoos! They share their name with birds in the family Cuculidae. Cuckoo birds lay their eggs in the nests of different species, often to the detriment of the host bird’s offspring. Same with the developing cuckoo bumblebee larvae. The field cuckoo’s larvae consume the food intended for the host colony’s offspring. Keep reading to learn why it is necessary for the field cuckoo bumblebee to rely on other bumblebee species to rear their young.

Five Facts about Field Cuckoo Bees

• Field cuckoo bumblebees are brood parasites
• Female cuckoos lay their eggs in established nests of other species
• Field cuckoos do not stay with their broods
• The nests of Bombus pascuorum, the common carder bee are used which to lay their eggs
• Field cuckoo bumblebees are a species of least concern

Scientific Name

Bombus campestris the scientific binomial name for the field cuckoo bumblebee literally translates to buzzing field. Bombus is Latin for buzzing, and campus is Latin for field, a reference to the habitat preference of field cuckoo bumblebees. Field cuckoos, as their name suggests, prefer fields and other open grassy areas. The genus Bombus is a reference to the characteristic buzzing of a bumblebee’s vibrating wings.

Appearance

The field cuckoo bumblebee has a distinctive appearance, with a yellow band around the middle of its body and dark wings. The head is black and the thorax has alternating bands of yellow and black. The abdomen is mostly black with splotches of yellow on the sides. Melanic, or dark-form individuals are not uncommon. Field cuckoos are medium-sized bumblebees. They measure between 0.5-0.7 inches long. Females of the species are larger than males. Characteristically absent are the pollen baskets, called corbiculae (singularly corbicula), which are essential to the task of keeping a brood alive.

Behavior

Field cuckoo bumblebees do not usually kill the host queen. However, the presence of cuckoo bumblebee larvae in a host nest can significantly reduce the viability of the host colony. In some cases, the increased competition for food and resources caused by the cuckoo bumblebee larvae can lead to the failure of the host colony. Field cuckoo bumblebees lay their eggs in the established nests, principally those of Bombus pascuorum, the common carder bee.

Habitat

Field cuckoo bumblebees are native to Europe and Asia. Field cuckoos are quite common in England and Wales. They are widespread throughout these regions and are commonly found in grasslands, meadows, and other open spaces. Flower-rich habitats are ideal.

Diet

As larvae, field cuckoo bumblebees consume the food stores (nectar and pollen) of the host colony, which they had intended to feed their own larvae. As adult bumblebees, field cuckoos feed on the nectar and pollen of flowering plants to obtain the energy and nutrients they need to survive and reproduce. Preferred nectar sources are thistle, dandelion, red clover, and ground ivy.. Males of the species will also forage on knapweed.

Predators and Threats

Habitat loss, climate change, pesticides, herbicides, disease, and competition for resources are among the threats to the continued existence of field cuckoo bumblebees. Increases in urban and suburban development reduce the availability of suitable habitats for field cuckoo bumblebees. Changes in temperature and precipitation, resulting from climate change, affect the timing and availability of food sources for field cuckoos. Either from direct exposure or from lingering contamination in the air and groundwater, pesticides and herbicides have debilitating effects on bumblebees. Diseases can destroy entire colonies of bumblebees. Nosema, a fungal disease causes gut infections and weakens the bee’s immune system. Deformed wing virus and acute bee paralysis are viruses that can lead to colony collapse. Even healthy colonies of bumblebees must compete for food and resources with other species, native and invasive.

Conservation Status and Population

As of 2014, Bombus campestris is listed as a species of least concern on The IUCN Red List of Threatened Species. In the intervening years, research is finding that bumblebees are declining at concerning rates. It would follow that field cuckoo bumblebees are suffering a similar fate. Population estimates are not readily available. for several reasons including that, as a parasitic species, cuckoos are difficult to track and observe. Trends in the general bumblebee population, however, would suggest that Bombus campestris populations are declining. The declining bumblebee populations are due to habitat loss, agricultural chemicals, and disease. To stem their decline, conservation measures, such as protected habitats, will be required.

Lifecycle

The lifecycle of the field cuckoo bumblebee begins when the female cuckoo emerges in late spring to early summer in search of a nest in which to deposit her eggs. Once she has scouted the perfect nest, she infiltrates. The field cuckoo maintains a low profile for the next few days as she picks up the scent of the colony. Once she has been identified/accepted as a member, the female field cuckoo bumblebee deposits her eggs in the cells that have been prepared for the host’s eggs. The field cuckoo then departs the nest, never to return. A few days later, before the host’s eggs hatch, the cuckoo’s eggs hatch,. The cuckoo larvae consume the food stores intended for the host colony’s offspring. As they grow, the cuckoo larvae continue to rely on the resources the host colony offers.
After shedding their exoskeletons multiple times (a/k/a molting), the larvae become the pupae which will undergo metamorphosis, developing into adult bumblebees. From egg to emergence takes approximately 6-8 weeks. Environmental factors like location, rainfall, and availability of resources determine the precise schedule. Once the cuckoo’s offspring emerge from the nest, they are capable of fending for themselves, foraging on flowers. When fall rolls around, field cuckoo bumblebees seek shelter, individually, underground. when the mercury rises in the spring, the field cuckoo emerges to start the cycle all over again.

Up Next:

• Vestal Cuckoo Bumblebee
• Forest Cuckoo Bumblebee
• Barbut’s Cuckoo Bumblebee