What is a Bumblebee?

Bumblebee is also called tribe Bombini or humble-bee. It is a common name for any member of the insect tribe Bombini (order Hymenoptera, family Apida [bumblebee family]) and also spelt bumblebee. These bees take place over much of the world, but these are most common in temperate climates. They are absent from most of the lowlands of India and Africa and have been introduced to New Zealand and Australia to aid in the pollination of multiple flowering plants. Most of the authorities recognize two genera: Psithyrus, the parasitic bumblebees and Bombus, the nest-building bumblebees. Certain species are at times assigned to a third genus, Bombias. Up to 19 species of Bombus and 6 species of Psithyrus take place in Great Britain.

About Bumblebee and Its Characteristics

Bumblebee animals are hairy and robust, average up to 1.5 to 2.5 cm (around 0.6 to 1 inch) in length, and are usually black with orange or broad yellow bands. Often, they nest in the ground, commonly in the mouse nests or deserted birds. Bombus species are social bees; it means they live in organized groups. Every nest has drones (males), queens, and workers. Psithyrus species, which have no worker caste, enter Bombus nests to lay eggs, cared for by Bombus workers. The resemblance between the Bombus species and a Psithyrus species it parasitizes is often remarkable. Sometimes, the British species P. vestalis stings the Bombus queen to death. Then there are no Bombus larvae to compete for the workers' attention with the parasitic Psithyrus larvae.

A Bumblebee (Bombus pennsylvanicus) represented below:

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After hibernating for the winter, the Bombus queen returns to the bumblebee nest to lay eggs. Generally, the first brood develops into 4 to 8 worker bees. Shortly after emerging as adult bumblebees, these specific workers take over the queen from the duties of pollen collection and caring for the hive. Then, the queen retires to a life of laying eggs. For a while, only the worker progeny are produced, and the colony grows until it has 50 to 600 bees. During late summer, with the wider population of workers bringing in abundant food, new queens and males are produced.

The below figure represents the bumblebee life cycle.

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Although a few males develop from unfertilized eggs laid by the queen, most of them hatch from eggs laid by workers. During early fall, the queen stops laying eggs, and gradually, the colony, including the queen, dies out. In this period, the larvae of certain moths and beetles usually prey on the remaining eggs and larvae in the bumblebee nest.

A Bumblebee (Bombus) is figured below.

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The queens of next season have developed from eggs laid late in the season. When fully grown, the future queens leave the bumblebee nest, mate, and find a sheltered place where to hibernate for the winter. Then, the lone queens start new nests in the following spring.

General Description

Bumblebee animals differ in appearance, but they are generally plump and densely furry. They are broader, larger and stouter-bodied than the honeybees, and their abdomen tip is more rounded. Several species have broad bands of colour, the patterns helping to differentiate various species. Whereas honeybees contain short tongues and thus majorly pollinate open flowers, some bumblebee species contain long tongues and collect nectar from the flowers, which are closed into a tube.


Bumblebees hold either none or fewer stripes and usually have part of the body covered with black fur, while honeybees hold several stripes, including many grey stripes on the abdomen. Sizes are much different even within species; the largest British species, B.terrestris, hold queens around 22 mm (0.9 inches) long, males around 16 mm (0.6 inches) long, and workers between 11 - 17 mm (0.4 - 0.7 inches) long. B.dahlbomii of Chile is the world's largest bumblebee species, measuring up to 40 mm (1.6 inches) in length and described as "a gigantic fluffy ginger beast" and "flying mice."

Distribution and Habitat

Typically, bumblebees are found in temperate climates, and they are often found at higher altitudes and latitudes than the other bees, although some lowland tropical species exist. Some species (B. alpinus and B. polaris) range into very cold climates, whereas the other bees might not be found; B. Polaris takes place in northern Ellesmere Island in the high Arctic, along with the other bumblebee B. hyperboreus that parasitises its nest.


This is defined as the northernmost occurrence of any eusocial insects. One reason for their presence in cold places is given as bumblebees may regulate their body temperature via solar radiation, which is the internal mechanisms of "shivering" and radiative cooling from the abdomen (known as heterothermy). The other bees have the same physiology, but the mechanisms seem best developed and have been most studied in the bumblebees.


They adapt to the higher elevations by extending their amplitude of wing stroke. Bumblebees contain a largely cosmopolitan distribution, but they are absent from Australia (apart from the Tasmania region where they have been introduced) and are found in Africa only in north Sahara. Also, a hundred plus years ago, they were introduced to New Zealand, where they play an essential role as efficient pollinators.

Biology

Feeding

The bumblebee tongue (called a proboscis) is a hairy structure and long that extends from a sheath-like modified maxilla. The major action of the tongue is lapping, which means repeated dipping of the tongue into the liquid. The tongue's tip probably acts as a suction cup and during lapping, nectar can be drawn up the proboscis by the capillary action. When flying or at rest, the proboscis is kept folded under its head.


The longer the tongue, the deeper the bumblebee may probe into a flower and the bees probably learn from the experience which flower source is best suited to the length of their tongue. Bees having shorter proboscides, like Bombus bifarius, holds a more difficult time foraging nectar relative to the other bumblebees with longer proboscides; to overcome this specific disadvantage, B. bifarius workers were observed to lick the spurs' back on the nectar duct, resulted in a small reward.

The figure given below represents a common carder bumblebee Bombus pascuorum by extending its tongue towards a Heuchera inflorescence.

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Wax Production

The abdomen's exoskeleton is divided into plates known as ventral sternites and dorsal tergites. Wax is secreted from the glands on the abdomen and is extruded between the sternites, where it resembles the dandruff flakes. It is secreted by the queen when it starts a nest and by the young workers. It is scraped from the abdomen by legs, moulded until malleable and is used in the construction of honeypots to cover the eggs, to line empty cocoons for use as storage containers and at times to cover the exterior part of the nest.

Colouration

The bumblebee's brightly coloured pile is an aposematic (warning) signal, given that females may inflict a painful sting. Based on the morph and species, the warning colours range from entirely black to red, bright yellow, white, orange, and pink. Dipteran flies in the families Asilidae (called robber flies), Syrphidae (called hoverflies), Oestridae (called warble flies or bot), Tabanidae (called horseflies) and Bombyliidae (called bee flies, such as Bombylius major) all include the Batesian mimics of bumblebees, resembling them closely enough to deceive at least a few predators.


The figure given below shows the Cuckoo bumblebees, like this Bombus barbutellus, contain the same aposematic (warning) colouration to nest-making bumblebees and can also mimic their host species.

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Communication and Social Learning

Bumblebees do not hold ears, and it is not known whether or how well they may hear. However, they are sensitive to the vibrations made by the sound travelling through wood or other materials.

Bumblebees do not exhibit "bee dances," which are used by the honeybees to share with other workers the food source locations. Instead, when they return from the successful foraging expedition, they run excitedly around in the nest for a number of minutes before going out to forage again. These bees can offer some form of communication based on the buzzing sounds made by their wings that can stimulate other bees to start foraging. Another stimulant to foraging activity is given as the level of food reserves in the colony. Bees monitor the honey quantity in the honeypots, and when a little is left or when high-quality food is added, they are likely to go out to forage.

Reproduction

Nest size will be based on the species of bumblebee. Most form the colonies of between 50 and 400 individuals, but colonies have been documented as smaller ~20 individuals and larger as 1700. These nests are smaller than the honeybee hives that hold up to 50,000 bees. Several species nest underground, choosing sheltered places or old rodent burrows, and avoiding places, which receive direct sunlight that could result in overheating.


The other species make nests above ground, whether in holes of trees or in thick grass. A bumblebee nest is not organized into hexagonal combs like the honeybee; instead, the cells are clustered together untidily. The workers remove larvae or dead bees from the nest and deposit them outside to the nest entrance, helping to prevent the diseases. In temperate regions, nests last only for a single season and do not survive the winter.

FAQs on Bumblebee

Q1. What are Asynchronous Flight Muscles?

Answer: Bees' wings can beat up to 200 times per second. Their thorax muscles do not contract on every nerve firing but rather vibrate like the plucked rubber band. This is efficient since it allows the system consisting of muscle and the wing operates at its resonant frequency, leading to less energy consumption.


Moreover, it is necessary since insect motor nerves cannot fire 200 times per second, generally. These types of muscles are known as asynchronous muscles and they are found in the insect wing systems in families such as Diptera, Hymenoptera, Hemiptera and Coleoptera. Bumblebees should warm up their bodies considerably to get airborne at the low ambient temperatures. Using this method, bumblebees may reach an internal thoracic temperature of 30 °C.

Q2. Explain about Cuckoo Bumblebees.

Answer: Bumblebees of the subgenus Psithyrus (called 'cuckoo bumblebees,' and formerly considered as a separate genus) are brood parasites, sometimes known as kleptoparasites, in the colonies of the other bumblebees and have lost the ability for pollen collection. Before finding and invading the host colony, a Psithyrus female, such as the Psithyrus species of B. sylvestris, feeds directly from the flowers.


Once she has infiltrated the host colony, the Psithyrus female subdues or kills the queen of that colony and uses pheromones and physical attacks to force the workers of the same colony to feed her, including her young. Usually, cuckoo bumblebees can be defined as queen-intolerant inquilines since the host queen is often killed to enable the parasite to form more offspring, though a few species, such as B. bohemicus, actually enjoy increased success when they leave the host queens alive.

Q3. What is a Pile?

Answer: Bumblebees contain round bodies covered with soft hair known as a pile, making them appear and feel fuzzy. They have aposematic (or warning) colouration, often consisting of contrasting bands of colour, and various species of bumblebee in a region often resemble themselves in mutually protective Müllerian mimicry. Often, harmless insects such as hoverflies derive protection from resembling bumblebees in Batesian mimicry, and it may be confused with them. 


Nest-making bumblebees can be differentiated from the same large, fuzzy cuckoo bees by the female hind leg form. In nesting bumblebees, it is modified to form the pollen basket, which is a bare shiny area surrounded by a fringe of hairs that are used to transport pollen, but, in cuckoo bees, the hind leg is hairy all around, and they never carry pollen.

Q4. Explain the Growth of Bumblebees.

Answer: The majority of bumblebees are social insects that live in colonies with a single queen. The colonies are smaller compared to the honey bees, growing to as few as 50 individuals in the nest. 


Cuckoo bumblebees are brood parasitic and they do not make nests; aggressively, their queens invade the nests of the other bumblebee species, kill the resident queens and after that, lay their own eggs, cared for by the resident workers. Previously, the Cuckoo bumblebees were classified as a separate genus, but now they are usually treated as members of Bombus.

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