They have aposematic (warning) coloration, often consisting of contrasting bands of colour, and different species of bumblebee in a region often resemble each other in mutually protective Müllerian mimicry.

[1] The generic name Bombus, assigned by Pierre André Latreille in 1802, is derived from the Latin word for a buzzing or humming sound, borrowed from Ancient Greek βόμβος (bómbos).

From experiments which I have tried, I have found that the visits of bees, if not indispensable, are at least highly beneficial to the fertilisation of our clovers; but humble-bees alone visit the common red clover (Trifolium pratense), as other bees cannot reach the nectar.However, "bumblebee" remained in use, for example in The Tale of Mrs. Tittlemouse (1910) by Beatrix Potter, "Suddenly round a corner, she met Babbitty Bumble--"Zizz, Bizz, Bizzz!"

Sophie Cardinal and Bryan Danforth comment that "While remarkable, a hypothesis of dual origins of advanced eusociality is congruent with early studies on corbiculate morphology and social behavior.

The only Bombus relatives in Bombini are the late Eocene Calyptapis florissantensis from the Florissant Formation, USA, and Oligobombus cuspidatus from the Bembridge Marls of the Isle of Wight.

[25] One reason for their presence in cold places is that bumblebees can regulate their body temperature, via solar radiation, internal mechanisms of "shivering" (called heterothermy), and countercurrent exchange to retain heat.

Depending on the species and morph, the warning colours range from entirely black, to bright yellow, red, orange, white, and pink.

For example, in California a group of bumblebees consists of largely black species including B. californicus, B. caliginosus, B. vandykei, B. vosnesenskii, B. insularis and B. fernaldae.

In a 2017 study involving Bombus terrestris, bees were taught to complete an unnatural task of moving large objects to obtain a reward.

(Psithyrus) vestalis, genetic analysis of individuals captured in the wild showed that about 42% of the host species' nests at a single location[a] had "[lost] their fight against their parasite".

[94] The great grey shrike is able to detect flying bumblebees up to 100 m (330 ft) away; once captured, the sting is removed by repeatedly squeezing the insect with the mandibles and wiping the abdomen on a branch.

The tree bumblebee B. hypnorum has spread into the United Kingdom despite hosting high levels of a nematode that normally interferes with queen bees' attempts to establish colonies.

[109] Bumblebee species are declining in Europe, North America, and Asia due to a number of factors, including land-use change that reduces their food plants.

Mechanisation removed the need for horses and most of the clover; artificial fertilisers encouraged the growth of taller grasses, outcompeting the meadow flowers.

The European Food Safety Authority ruled that three neonicotinoid pesticides (clothianidin, imidacloprid, and thiamethoxam) presented a high risk for bees.

[113] While most work on neonicotinoid toxicity has looked at honeybees, a study on B. terrestris showed that "field-realistic" levels of imidacloprid significantly reduced growth rate and cut production of new queens by 85%, implying a "considerable negative effect" on wild bumblebee populations throughout the developed world.

[115] In another study, chronic exposure in a laboratory setting to field-realistic levels of the neonicotinoid pesticide thiamethoxam did not affect colony weight gain or the number or mass of sexuals produced.

[128] In South America, Bombus bellicosus was extirpated in the northern limit of its distribution range, probably due to intense land use and climate change effects.

"[130][131] In 2009 and 2010, the Trust attempted to reintroduce the short-haired bumblebee, Bombus subterraneus, which had become extinct in Britain, from the British-derived populations surviving in New Zealand from their introduction there a century earlier.

[132] From 2011, the Trust, in partnership with Natural England, Hymettus and the RSPB, has reintroduced short-haired bumblebee queens from Skåne in southern Sweden to restored flower-rich meadows at Dungeness in Kent.

Agri-environment schemes spread across the neighbouring area of Romney Marsh have been set up to provide over 800 hectares of additional flower-rich habitat for the bees.

John H. McMasters recounted an anecdote about an unnamed Swiss aerodynamicist at a dinner party who performed some rough calculations and concluded, presumably in jest, that according to the equations, bumblebees cannot fly.

[138] In later years, McMasters backed away from this origin, suggesting there could be multiple sources, and the earliest he has found was a reference in the 1934 book Le Vol des Insectes by French entomologist Antoine Magnan (1881–1938); they had applied the equations of air resistance to insects and found their flight was impossible, but "One shouldn't be surprised that the results of the calculations don't square with reality".

[139] The following passage appears in the introduction to Le Vol des Insectes:[140] Tout d'abord poussé par ce qui se fait en aviation, j'ai appliqué aux insectes les lois de la résistance de l'air, et je suis arrivé avec M. Sainte-Laguë à cette conclusion que leur vol est impossible.

This ignores the effect of dynamic stall (an airflow separation inducing a large vortex above the wing), which briefly produces several times the lift of the aerofoil in regular flight.

[143] Additionally, John Maynard Smith, a noted biologist with a strong background in aeronautics, has pointed out that bumblebees would not be expected to sustain flight, as they would need to generate too much power given their tiny wing area.

[149] Emily Dickinson made a bumblebee the subject of her parody of Isaac Watts's well-known poem about honeybees, "How Doth the Little Busy Bee" (1715).

",[150] Dickinson's poem, "The Bumble-Bee's Religion" (1881), begins "His little Hearse-like Figure / Unto itself a Dirge / To a delusive Lilac / The vanity divulge / Of Industry and Morals / And every righteous thing / For the divine Perdition / of Idleness and Spring."

[153] His daughter, the poet Sylvia Plath, wrote a group of poems about bees late in 1962, within four months of her suicide,[154] transforming her father's interest into her poetry.

[155] The scientist and illustrator Moses Harris (1731–1785) painted accurate watercolour drawings of bumblebees in his An Exposition of English Insects Including the Several Classes of Neuroptera, Hymenoptera, & Diptera, or Bees, Flies, & Libellulae (1776–80).