Heath Bumblebee (Bombus jonellus)
The fairly small-sized Heath bumblebee (Bombus jonellus), also called small Heath bumble bee, is widespread in Europe, northern America, and northern Asia. It is more common north of 55ºN, and less widespread in southern latitudes.
Although it falls into the white-tailed bumble bees category, in the Shetland and Western Isles male variations of this species can also have an orange tail. These orange-tailed Heath bumble bees closely resemble the Early bumble bee (Bombus pratorum).
The small Heath bumble bee looks very similar to the larger Garden bumblebee (Bombus hortorum) and the rarer Ruderal bumblebee (Bombus ruderatus). Their faces tell them apart. Whereas the later two species have longer, thinner faces, the Heath bumblebee´s face is almost completely round. Another similar-looking species is the Barbut´s cukoo bumble bee (Bombus barbutellus), a parasite of the Garden bumblebee. This bumble bee´s face is also round, but it has no pollen baskets that could differentiate it from the females.
Heath bumble bees have a short proboscis (tongue). The coloring of this species is identical across all three casts. The only difference to tell the casts apart is their size. All have a yellow thorax followed by a large black band. The thorax has a large yellow stripe that is separated by a thinner black band. Drones can be identified by their bright yellow face. These bumble bees look somewhat shaggy or unkempt.
Habitat of the Heath Bumblebee
As the name suggests, it typically makes its habitat in heathland but is also found in gardens, meadows and moorlands. Their preferred flowers to forage include Dandelion, Bilberry, Heather, clover, bird’s-foot trefoil, cowberry, thistles, Vetches, Knapweed, and other flowers.
Heath bumble bees can be located above or below ground. Their nests can be situated in various locations, underground in small rodent nests, within heaps of leaves or moss, and above ground in old birds’ nests. Heath bumble bees have also been observed to make their nest in roof spaces.
Heath Bumble bee colonies typically consist of less than 50 workers, but can have as many as 120 workers. Depending on the climate these bumble bees can have two broods per season.
The lifecycle of bumble bees begins in late winter or early spring (March) when a fertilized queen exits diapause. To replenish her energy reserves and promote the development of her ovaries, she consumes pollen and nectar while searching for a suitable nest site. Once a nest site is found, the queen builds a single nectar pot from the wax she produces. The pot is filled with a mixture of pollen and nectar to provide her with energy.
She then lays her first batch of eggs, which typically consist of 6-16 eggs. The queen incubates the eggs with her own body heat, and after 3-5 weeks, they develop into larvae and eventually pupate. When the queen’s first worker offspring emerges, they take on foraging and brood-rearing responsibilities to allow the queen to focus on laying more eggs. At this stage, the bumble bee colony is comprised of a single queen, female workers, and immature brood.
New Queens and Drones
New queens and males start to emerge when the colony has reached a sufficient quantity. Their emergence signals the beginning of the end of the colony. The old queen and the workers die naturally around autumn time (September/early October).
Once fully developed, the new queens and drones leave the nest to mate. Soon after mating with the new queens, the drones die, whereas the new fertilized queens find space to hibernate over winter and the cycle repeats itself.
A Swedish study discovered that although heath bumble bees typically fly closer to the ground, the drones patrol circuits at tree-top hight to deposit pheromones on leaves and branches to attract new queens. The actual mating process may take place on the ground or on vegetation.
Predators and Diseases of the Heath Bumble Bee
Badgers, the primary mammalian predators, actively use their sharp claws to uncover nests. Especially in arid conditions, predation becomes more likely due to badgers having a tougher time foraging for worms, which is their preferred food. B
Birds play a significant role in reducing bumblebee populations. Some of the most common bird predators include cuckoos and great tits that feed on the brood. Adult bumblebees also fall prey to some birds, like magpies and corvids. Studies reveal that the number of bumblebee nests under bird attack increases during a shortage of their preferred food. This indicates a greater predation pressure from birds during food-scarce years. In summary, the impact of bird predation on bumblebees underscores the need for conservation measures to protect dwindling bee populations.
Other threats can include wasps, flies and spiders but also the Forest cuckoo bumblebee (Bombus sylvestris), which attacks the Heath bumble bees nests. The biggest threat however are humans destroying their habitat and using dangerous pesticides.