Bombus fervidus

Danish zoologist Johan Christian Fabricius first identified Bombus fervidus, also known as the yellow bumblebee or golden northern bumblebee, in 1798. B. fervidus is a member of the order Hymenoptera, which comprises wasps, ants, bees, and sawflies. Bombus is the Latin word for "buzzing". It is also in the Apidae, which is a diverse family of bees including honeybees, orchid bees, bumble bees, stingless bees, cuckoo bees, and carpenter bees. It is very closely related to Bombus californicus, and in many areas of geographic overlap, at least a small percentage of individuals of the two species cannot be recognized except by genetic analysis, as each species can sometimes display the color pattern typical of the other.[2]

Bombus fervidus is on average 13–16 mm long[3] However, there are slight differences in morphology between queens, workers, and drones (see table below).[4] The first four abdominal tergites are yellow.[5] The occiput and face are black, and have yellow pleurae extending to or nearly to the bases of the legs. A black band is present between the base of wings. The wings are dark to dark grey colored. The hairs are thick. B. fervidus is long-tongued and therefore specializes on flowers with long corollas.[6] B. fervidus use long tongues to extract nectar and pollen from longer flowers.[7] Males have slightly more yellow on their abdomen, and are difficult to distinguish from B. pensylvanicus and B. californicus. Males have a wingspan of 22 mm while female workers have a wingspan of 40 mm.[8]

B. fervidus is native to Canada, Mexico and the continental United States,[9] and individuals in its genetic lineage are more broadly distributed than previously suspected.[2]

The species prefers temperate savanna, grassland and tall grass biomes, and readily coexists with suburban or agricultural developments. It is common in grazing farmlands.[10][11]

Bombus fervidus queens lay eggs individually in cells within the nest that she builds herself.[7] She first lays 8-10 eggs, one in each cell. When these eggs hatch, the larvae emerge and feed on honey for growth.[7] The queen makes the honey for the larvae until they are ready to pupate, which is when the larva create cocoons for themselves where they stay to metamorphose into adults.[7] Metamorphosis typically takes 16 to 25 days.[8] Once the adults bees emerge from the cocoon, they are adult workers.[8] This first generation of the brood that becomes workers are responsible for feeding the next generation of developing larvae and the queen. This ensures that the queen can focus on laying more eggs.[7] Thus, each generation of B. fervidus is larger than the one before it.[7][8]

Male bumblebees, also known as drones, have a purely reproductive purpose.[7] In the fall, males and newly hatched queens mate before the weather cools. Each future queen mates only once and stores the sperm for the remainder of her life, using it to produce all the subsequent female progeny. After mating, young queens hibernate underground until the spring while all the other bees will die. The queens then emerge from hibernation and feed on pollen and nectar until they can lay their first brood of 8 to 10 eggs.[8] Before laying the eggs, they build a nest out of grass and deposit honey into a wax honey pot that she made.[7][8] They make and deposit honey in the honey pot after collecting enough pollen.[11] Breeding occurs in the summer months.[7] Most workers live for a brief period of time due to the intensity of their work, while queens live for 12 months on average.[8] B. fervidus workers are responsible for making the honey that the queen and developing brood eat.[7] The workers chew pollen and mix it with their saliva to make the honey. Since they need ample pollen for honey, workers spend a lot of time foraging for nectar and pollen, simultaneously pollinating flowers. When a worker emerges from its cocoon, it will devote most of its time toward developing the brood and consequently building a larger nest out of grass to accommodate the growing colony.[7] If the colony grows too big, then new queens are sometimes killed before it is time for them to mate. Males have a purely reproductive purpose in the nest.[8] Most B. fervidus do not live for more than a few months due to the toll hard work takes on the body and harsh winter weather. Only the queens live for approximately one year.[8]

Bombus fervidus workers are able to feed both the queen and the developing brood by chewing/mixing pollen and saliva. In order to have enough of this food, B. fervidus spend a lot of time foraging for pollen and nectar, pollinating flowers in the process.[7] Thus they have an important role in the ecosystem.

When a new worker bumblebee emerges from its cocoon, it takes care of the queen and her eggs. Although the queen started the colony on her own, new workers will accommodate the growth of the colony by adding dead grass to the nest. If the population grows too big, newly emerged queens may arise that must leave the nest early or even be killed by other workers before they mate.[7]

Because males have a purely reproductive process in the nest, they will often leave the nest. They live independently until the fall, when they mate and then die.[11]

One very successful parasite of many Bombus species is Bombus ashtoni.[7] It lives within the nest and eats the eggs of its host. Consequently, the host workers care for the brood of the parasite instead of their own.[7] The earlier this parasite enters the host nest, the longer it will wait before laying its eggs.[16] Eggs are laid during the growth phase of workers in their colony cycle, which results in a reduced number of workers reared in the nest.[16] This replacement of host eggs with parasite eggs is a gradual process as a strategy in which there is an overlap between the colony investment of both species.[16]

The greatest role of Bombus fervidus in the ecosystem is as a pollinator of many flowering plants.[8] Thus, as a species, B. fervidus has a positive influence on humans as these bees help to pollinate many flowers, including major plant crops that are harvested as food.[7][8] One negative influence of B. fervidus on humans is that as a defense mechanism this bee will sting a human immediately when it perceives a threat.[7]

Like most bumblebees, Bombus fervidus is in decline and in need of protection. Abundance declines have been observed across most of North America; the most apparent threat is the loss of its preferred grassland and tallgrass habitats to agricultural intensification. It is currently classified as vulnerable by the IUCN.[1]