Bumble Bees

Buff-tailed Bumble Bee, Photo Courtesy of Pim Lemmers

Bumble bees (or bumblebees) are some of the most recognizable and beloved of all bee species. With their cute, distinctive fluffy yellow to orange and black fur markings, they often appear in cartoons and movies. Bumblebees are famous for their peculiar, ‘bumbling’ flight patterns, and their characteristic buzzing sound where the Latin name Bombus (literally meaning ‘booming’) comes from. The famous buzz is not just to communicate, it also helps to pollinate plants that do not create nectar.

Unlike honeybees, bumblebees do not produce honey to store as food in preparation for the winter months.

The abundance of bumblebees in urban areas and gardens may seem surprising given their size. This is because these resilient creatures continually adapt to new environments. They take advantage of a variety of food sources including flower nectar or sugary liquids like overripe fruits.

Not only do bumble bees help to keep our food supply alive and healthy, but they also control pest populations. Bumble bee colonies can have up to 400 individual bees, which helps them to search out and hunt down pesky insects like aphids.

Genus and Distribution

These large Hymenoptera belong to the family Apidae. They include cuckoo, carpenter, digger, bumble, and honey bees. Scientifically they are referred to as Bombus spp. There are as many as 300 species of bumble bees across the globe. In Europe, there are an estimated 68 species, with 124 species in China, 24 species in South America and 49 species across the United States. To identify a bumble bee, click here.

Bumblebees are a type of eusocial insect that is found all over the world. They are typically in temperate climates and latitudes that are higher than other species of bees. For example, B. polaris and B. alpinus are capable of surviving in very cold climates where other bees could not exist, such as northern Ellesmere Island in the high Arctic. This is the northernmost occurrence of any eusocial insect.

Bumblebees are found worldwide, with the exception of Australia (apart from Tasmania where they have been introduced), and Africa north of the Sahara.

The important role of bumblebees in pollination makes understanding the biology, distribution, and conservation even more crucial. Therefore, further research is needed to ensure the continued survival of these important species.

Bumble Bees are Heterothermic

Bumblebees can regulate their body temperature with solar radiation. These are internal mechanisms of “shivering” and radiative cooling from the abdomen (called heterothermy). The unique ability allows bumblebees to employ counter current heat exchange, a technique where the thorax (mesosoma) retains heat, while the abdomen (metasoma) loses heat. This process is accomplished through a constriction of muscles at the point where the thorax and abdomen meet. It enables the internal temperature of a honeybee’s thorax to exceed 45C (113F) while in flight.

It enables bumble bees to survive in areas that would otherwise be too cold for other species, because they can adapt to higher elevations by increasing the amplitude of their wing strokes. Other types of bees have similar physiologies, but the mechanisms are best developed and studied in bumblebees.

How are Bees Categorized?

It is sometimes easy to get confused about what a tribe, a family, or a genus is. The proper categorization is divided in Order, Family, Subfamily, Tribe and Genus. In the example below, the Order Insecta is a larger group that includes all insects. From there, it gets more specific as you move down to Family, Subfamily, Tribe, and Genus. The Family is Apidae which includes all bees: honey bees, bumblebees, and carpenter bees. The Subfamily is Apinae which includes just honey bees and bumblebees. The Tribe is Apini which is just honey bees. Finally, the Genus is Apis which specifically includes just the honey bee. In essence, each classification is a little more specific than the one before i.:

Order: Insecta

Family: Apidae (honey bees, bumblebees, carpenter bees)

Subfamily: Apinae (honey bees, bumblebees)

Tribe: Apini (honey bees)

Genus: Apis (honey bee)

What do Bumble Bees look like?

Bumblebees are one of the more recognizable bees because of their cute plump and densely furry bodies. Their soft hair (pile) makes them look fuzzy and fluffy. They are usually bigger, broader, and stouter than honeybees, and their abdomen tips have a more rounded shape. Bumble bees usually have black and yellow (sometimes orange) colored bands. These bands not only serve as a warning sign, they also help identify the different species. Bumblebee species either have fewer stripes than honey bees or none at all, although their bodies is also covered in black fur. The unique patterns help distinguish different types of bumblebees from each other.

How big are Bumble Bees?

The sizes of bumblebees can also vary significantly between different species, although the average length is between 1.5 to 2.5 cm (about 0.6 to 1 inch). Queens of the B. terrestris species, the largest British bumblebee species are up to 22 mm (0.9 in) long, whereas males are up to 16 mm (0.6 in) long. Their workers can range from 11 to 17 mm (0.4-0.7in). The largest bumblebee species worldwide is the B. dahlbomii, which is found in Chile and can grow up up to 40mm (1.6in).

Nest-making bumblebees can be identified from similarly large fuzzy cuckoo bees by the females hind legs. Whereas the hind legs of nesting bumble bees have a pollen basket, the hind legs of cuckoo bees are hairy overall because they do not carry pollen. Another difference to honey bees is the size of their tongue (proboscis). While honeybees have very short tongues, some bumblebee species have long tongues allowing them to reach nectar in closed tubes.

Many species of bumblebee can create special vibration or buzzing sounds with their wings. This serves to communicate within the colony, such as alerting others about potential threats or food sources located nearby.

Short- and Long Tongued Bumble Bees

Short-tongued Bumble Bee

Bees can be split into two (sometimes 3) different groups, based on the length of their proboscis (tongue): short, (medium), and long. Long-tongued bees have longer tongues to reach deep down into flowers to get the nectar. Short-tongued bees have shorter tongues to feed on the nectar of shallow-throated flowers. This variation in tongue size is what allows bumblebee species to feed from flowers of varying sizes and shapes. It allows them to maximize the amount of pollen they collect and disperse to other plants.

Long-tongued Bumble Bee

The bumble bees’ tongue and mouth are covered in numerous microscopic hairs (papillae). These papillae have numerous tiny pores that allow molecules to pass through. The molecules attach themselves to receptor sites on the sensory cells located in the tongue.

When these molecules bind, they stimulate nerve impulses that travel along the bee’s olfactory nerves to the brain. This triggers an electrochemical reaction in the brain, allowing the bee to “taste” or recognize a particular molecule. The bee can then use this information to identify and learn to recognize food sources. In addition, it can use this information to find and remember the location of certain flowers it visited previously. When the bee rests or flies, they keep their tongue folded under their head.

Unique Pollination Method

Bumble bees are highly important pollinators, independent of their tongue-length. Their unique behavior of buzzing, or sonicating, is important for flowers that require this type of pollination. Certain flowers, such as tomatoes and other members of the plant family of Solanaceae, do not produce nectar, but the bees still visit these flowers in order to collect pollen. This is done by the bee vibrating its wing muscles, making a buzzing sound, which shakes out the pollen grains from the anthers.

Are Bumble Bees Endangered?

Once widespread across much of the United States, the American bumblebee has seen an alarming and drastic reduction in numbers over the past two decades. It was once common in open prairies, grasslands and urban areas across the US, but has since suffered a severe decline. Recent estimates suggest that its range has been reduced by almost 90%! It is now absent or very rare in 16 states.

In 2021, a petition was submitted to grant endangered Species Act protection to the American bumblebee (Bombus pensylvanicus)), the Crotch’s bumble bee (Bombus Crotchii), Franklin’s bumble bee, Suckley’s cuckoo bumble bee (Bombus suckleyi) and the western bumble bee (Bombus occidentalis) be listed as endangered species under CESA. Currently, only two bumblebees, the rusty patched bumblebee and the Franklin’s bumble bee are protected under the Act.

The endangered Franklin’s bumblebee (Bombus franklini), is the rarest species of bumblebee in the world. Once found in southern Oregon and the most northern parts of California, the species has not been sighted since 2006.


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