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Buff-tailed Bumblebee - Bombus terrestris
Buff-tailed Bumblebee - Bombus terrestris

[Image: Buff-tailed-bumblebee.jpg]

Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Apidae
Subfamily: Apinae
Genus: Bombus
Subgenus: Bombus
Species: Bombus terrestris

Bombus terrestris, the buff-tailed bumblebee or large earth bumblebee, is one of the most numerous bumblebee species in Europe. In addition, Bombus terrestris is the largest of the European bumblebee species. It is one of the main species used in greenhouse pollination, and consequently, can be found in many countries and areas where it is not native, such as Tasmania for example. Moreover, it is a eusocial insect that is characterized by unique Hymenopteran sex ratios, where male drones dominate most colonies. The queen of B. terrestris is often highly dominant over her colony, and exhibits behaviors such as altering the sex ratio in her favor over the workers and controlling queen larval development with pheromones. However, after aggression breaks out in the nest, the workers can usually gain control of the nest and restart the colony cycle. The queen is monandrous and only mates with one male after leaving the nest, despite the potential genetic benefits from polyandrous mating. B. terrestris demonstrates noteworthy learning tactics with flower color and diverse foraging behaviors. They have also been implicated in a number of bee pathology studies investigating bee parasites and viruses.

Taxonomy and phylogenetics
B. terrestris is part of the order Hymenoptera, which is composed of ants, bees, wasps, and sawflies. The family Apidae specifically consists of bees. It is also part of the subfamily Apinae, which includes most species of bees. There are 14 tribe lineages within Apinae, and B. terrestris is in the bumblebee tribe, Bombini. It is in the genus Bombus, which consists entirely of bumblebees, and the subgenus Bombus sensu stricto. This subgenus contains closely related species such as Bombus affinisBombus cryptarumBombus frankliniBombus ignitusBombus lucorumBombus magnusBombus occidentalis, and Bombus terricola. There are nine recognised subspecies: B. terrestris africanusB. terrestris audaxB. terrestris calabricusB. terrestris canariensisB. terrestris dalmatinusB. terrestris lusitanicusB. terrestris sassaricusB. terrestris terrestris and B. terrestris xanthopus, each with a distinctive colouration scheme.

[Image: Buff-tailed-bumblebee-on-thistle-flower.jpg]

Description and identification
B. terrestris are pollen-storing bees that generally feed and forage on nectar and pollen. The queen is between 20–22 mm long, males range from 14–16 mm, and workers from 11–17 mm. The latter are characterized by their white-ended abdomens, and look just like workers of the white-tailed bumblebee, B. lucorum, a close relative, apart from the yellowish bands of B. terrestris being darker in direct comparison. The queens of B. terrestris have the namesake buff-white abdomen tip ("tail"); this area is white like in the workers in B. lucorumB. terrestris are unique compared to other bees in that their caste of workers exhibit a wide variation in worker size, with thorax sizes ranging from 2.3 to 6.9 mm in length and masses ranging from 68 to 754 mg.

Distribution and habitat
B. terrestris is most commonly found throughout Europe and generally occupies temperate climates. Because it can survive in a wide variety of habitats, there are populations in the near East, the Mediterranean Islands, and Northern Africa as well. Additionally, after being introduced as a greenhouse pollinator in nonnative countries, this bee is now considered an invasive species in many of these countries, including Japan, Chile, Argentina, and Tasmania. Nests are usually found underground, such as in abandoned rodent dens. Colonies form comb-like nest structures with egg cells each containing several eggs. The queen will layer these egg cells on top of one another. Colonies produce between 300-400 bees on average, with a large variation in the number of workers.

Colony structure
Social castes

Like in most social bees, there are three main social caste divisions in B. terrestris. This ensures a division of labor and efficient colony functioning. Queens become the main female individual to reproduce in a future colony. Her sole responsibility is to lay eggs after she founds a nest. This fate is determined for larvae that receive more food, have longer instar stages, and higher levels of juvenile hormone biosynthesis. Workers, an entirely female caste, mainly forage for food, defend the colony, and tend to the growing larvae. They are usually sterile for most of the colony cycle and do not raise their own young. Unlike queens and workers, which develop from fertilized diploid eggs, drones, or male bees, are born from unfertilized, haploid eggs. Drones leave the colony shortly after reaching adulthood to find a mate outside the nest. This is their sole role in the colony.

Life cycle
A solitary queen hatched from her abandoned colony initiates the colony cycle when she mates with a male and finds a nest. She will stay in this nest over winter and then will lay a small batch of diploid eggs in the spring. Once these hatch, she tends the larvae, feeding them with nectar and pollen. When the larvae are grown, they pupate, and about two weeks later, the first workers emerge. This is known as the initiation phase of the colony. Workers will forage for nectar and pollen for the colony and tend later generations of larvae. The workers are smaller than the queen, and only live for a few weeks. The foraging range and frequency of workers depends on the quality and distribution of available food, but most workers forage within a few hundred meters of their nest.

This first phase can last a variable amount of time in B. terrestris, after which the switch point is reached, and the queen begins to lay some unfertilized eggs, which develop into males. When the male drones emerge from the nest, they do not return, foraging only for themselves. They seek out new queens and mate with them. Remaining diploid eggs receive extra food and pupate to become new queens. The queen can use pheromones to discourage the workers' inclination to invest more in these larvae, thereby ensuring that not too many become queens. The colony persists until the competition point is reached, when workers begin egg laying. At this point, outright aggression among workers and between the queen and workers begins. This is a predictable time point that occurs about 30 days into the colony cycle.

Usually, the worker-queen conflict will force the queen out and the new workers will become queenless. A "false queen" might take control of the colony for a short period. The colony cycle starts again when the newly hatched queens leave the nest in search of a mate and a nest for themselves in order to start a new colony.

[Image: Buff-tailed-bumblebee-flying-from-spotte...nettle.jpg]

Reproductive behavior
Mating system

B. terrestris is thought to be a singly mating species. This is unusual for social insect queens because mating with several males (polyandry) has potential genetic benefits. The lack of multiple matings by B. terrestris queens may be partly due to male interference. B. terrestris males plug the female's sexual tract with a sticky secretion during mating, which appears to reduce the female's ability to successfully mate with other males for several days. It has also been suggested that when compared to singly mated queens, females that mate with multiple males have reduced hibernation success and fitness due to some harmful effect of sperm on the female. While there may be genetic fitness benefits in colony heterogeneity from a polyandrous mating system, bumblebees are also likely to be monandrous due to social constraints and risks associated with multiple matings. Finding multiple mates might be energetically costly and expose the queen to higher predation risks. Additionally, while queens may prefer multiple matings to ensure more genetic variability and viable offspring, the queen-worker conflict dictates that workers will be more apt to raise larvae from a single male. This is due to haplodiploidy in Hymenopteran social insects in which males (drones) are haploid and females (workers and queens) are diploid. This confers greater genetic similarity between sister workers (relatedness of 0.75) than between mother and offspring (relatedness of 0.5), making kin selection stronger between sisters. This selective force would be reduced if workers were the offspring of multiple males, which might lead to increased conflict in the nest.

Worker egg laying
In addition to the queen, the workers can lay eggs for the colony brood. Since workers do not mate, all of their eggs are haploid and will develop into drones. There are multiple factors that determine whether a worker bee will become reproductively active. Workers born early in the first brood are more likely to become egg layers due to their increased size and age, which allows more time for ovarian development. Workers usually have to be at least 30 days old to become an egg layer. Individuals that spend less time foraging and more time near the queen are also more likely to become reproductive. Lastly, due to intense competition for the opportunity to reproduce, older workers often harass the queen by attacking her and buzzing loudly. Once this point is reached the colony is usually abandoned.

Sex ratios
Due to the variability in the switch point of B. terrestris colonies, there are varying levels of sex ratios among nests. Early-switching colonies have a much smaller number of future queens compared to males (1:17.4), which may give them a competitive advantage in mating with later emerging queens. Late-switching colonies have fewer males and a more even sex ratio of 1:1:3, thus indicating the queen's control over her colony (she prefers a 1:1 ratio, since she is equally related to both sons and daughters). On the other hand, workers prefer a 3:1 ratio, as they are more related to each other than to their mother. Although early and late switching colonies are usually balanced equally in numbers in the population, the overall demographic in one study was found to be male biased, resulting in an overall sex ratio of 1:4 (female to males). However, most studies show that this balance of bimodal sex determination between early and late-switching colonies creates the queen's preferred 1:1 sex ratio in B. terrestris populations. This is unusual for monogamous social insects, which usually have a 3:1 sex ratio indicative of worker colony control. B. terrestris often does not conform to standard predictions of sex ratios based on evolutionary theory and haplodiploid theory.

[Image: Buff-tailed-bumblebee-in-flight.jpg]

Reproductive suppression
Queen suppression

Queen bees can control oogenesis in worker bees via juvenile hormone (JH), which regulates egg development. Among queenless B. terrestris workers, the corpus allata, which secretes JH, was noticeably enlarged compared to queenright workers. JH concentrations were also higher in the hemolymph of queenless workers. This suggests that the presence of a queen is enough to prevent workers from laying eggs, which helps her maintain genetic control over her colony's brood. The mechanism through which the queen induces this behavior is likely through pheromones.

Worker suppression
While the queen controls much of the egg laying and larval development in the colony, it is likely that workers play a much bigger role in controlling egg laying than previously thought. Dominant workers will often inhibit younger workers from laying eggs. Workers have low levels of JH and ovarian development during the early stages of the colony cycle and also after the competition point. Workers introduced into queenright and queenless colonies experience similar levels of inhibition from fellow workers during the competition point, indicating the key role of worker policing of fellow nest mates later in the colony cycle. This suggests that worker reproductive development will be highest between early development and the competition point in the colony.

Kin selection
Worker-queen conflict

Conflict is expected between queen and workers over the sex ratio and reproduction of males in the colony, especially in monandrous colonies where workers are more related to their own sons and nephews than to their brothers. In early-switching colonies, workers might start laying eggs when they know it will be in their own genetic interests, perhaps from a cue that indicates the switch point has been reached and the queen is now laying haploid eggs. This might be delayed, because sex can only be differentiated in mature larvae by workers. In late-switching colonies (where the competition point still occurs at the same time in the cycle), workers may start laying eggs when they detect a change in the queen’s pheromone that indicate larvae are developing into new queens. Thus, the outcome of this conflict is mediated through the dominance of the queen and the information available to the workers. While it is assumed that queens usually win this conflict, it is still unclear because some studies have indicated that up to 80% of males are produced by workers. These asymmetries in the timing of egg lying and dominance in B. terrestris might explain why it often does not conform to predicted sex ratios and kin-selection hypotheses.

Worker-worker conflict
Although B. terrestris workers are most directly in competition with the queen for egg laying opportunities, they will still inhibit their sisters from laying eggs in order to have their own sons. This is beneficial to them because they will share more genes with their own son (.5) rather than their nephews (.375). However, kin theory states that in monandrous colonies, workers will be most closely related to each other, so they should spend the most time raising the queen's young, which are their full sisters. This likely reduces worker-egg laying and worker policing, but it is still prevalent in B. terrestris, again indicating how this bumblebee often does not conform to standard kin selection theories for social insects. Worker policing is most common in polyandrous colonies, where sisters can be as removed from one another as they would be from a brother. This increases competition for egg laying and worker policing since nephews are more distantly related to each sister than in singly mated colonies. More research will likely need to be done in order to elucidate the underlying conflict in B. terrestris colonies.

[Image: Buff-tailed-bumblebee-covered-in-pollen.jpg]

Social and foraging behavior
Dominance hierarchy

Workers start out at the bottom of the dominance hierarchy in the social colony. As they age, they move closer to the position of queen. Queen-side workers are often egg layers and interact more frequently with the queen. This social position may pay off later, after the competition point is reached. When the queen is overthrown by the aggression of the workers, the most dominant worker will have the best likelihood of contributing more eggs to the colony brood and will perhaps climb to the position of “false queen.” The queen appears to maintain a constant distance of social dominance from her workers at all points in the cycle, suggesting that she is displaced by the sheer number of workers later in the cycle.

Foraging behavior
B. terrestris generally forage on a large variety of flower species. Their highest activity is in the morning, with their peak time being noted at around 7-8 am. This is likely because it gets progressively warmer in the afternoon, and foragers prefer ambient temperatures of around 25°C during nectar and pollen collection. 

B. terrestris bees exhibit alloethism, where different sized bees perform different tasks, in foraging behavior. Larger bees are more often found foraging outside the nest and will return to the nest with larger amounts of nectar and pollen. It is possible that larger bees might be able to withstand greater temperature variation, avoid predation, and travel larger distances making them selectively advantageous. Distinct social roles based on morphology might also be beneficial for individuals of the colonies, by making the colony operate more efficiently. Small bees can be reared more cheaply and kept for in-nest tasks, while only some larvae will be fed enough to become large foraging bees.

Food alert
Individuals who return from the nest after a foraging run often recruit other bees in the colony to leave the nest and search for food. In B. terrestris, successful foragers will return to the nest and run around frantically and without a measurable pattern, unlike the ritualized dance of the honeybee. Although the mechanism by which this recruitment strategy functions is unclear, it is hypothesized that running around likely spreads a pheromone that encourages other bees to exit and forage by indicating the location and odor of food nearby. It is worth noting that colonies with lower food stores will often be more responsive to this foraging pheromone. Conversely, in colonies with ample food reserves bees will be less responsive to these pheromones likely to save time and energy from unnecessary foraging. 

Homing ability
B. terrestris has an impressive homing range, where bees displaced from their nests can relocate the colony from up to 9.8 km away. However, the return often takes several days, indicating B. terrestris might be utilizing familiar foliage and natural landmarks to find the nest. This may be a tedious process if an individual is outside the conventional foraging range of the nest. Another study indicated that these bees can navigate their way back to the nest from a distance as far away as 13 km (8.1 mi), although most forage within 5 km of their nest. One mark and recapture study found their average foraging distance to be approximately 663 m. Male bees have also been found to have longer flight ranges than worker bees, likely because they move farther away from the nest to find mates. Males have flight distances of anywhere from 2.6-9.9 km. If males also contribute to pollination, this might increase previously predicted pollen flow ranges based on worker flight behavior.

Bumblebees and honey bees are extremely influenced by an innate preference for blue and yellow color. When they have no training, they will often just visit flowers that naturally attract them. However, it is generally thought that bees will learn to visit more nectar rewarding flowers after experience associates the reward with the color of the petals. This has been demonstrated in B. terrestris, where bees trained on artificially colored flowers will pick a similar color to the one they were trained with when tested with an array of flower choices. If individuals were tested with flower colors significantly different than from what they were trained with, they just visited flowers most closely aligned with their innate color preferences. In addition to identifying specific colors for foraging purposes, it has also been shown that young worker bees have to learn complex motor skills in order to efficiently collect nectar and pollen from flowers. These skills might take several days to develop, as memory does not always hold perfectly on a day-to-day basis, sometimes deteriorating overnight. It is worth noting that even within a species different populations have varying levels of innate blue preference and exhibit intraspecific variation in learning rate during association tasks. This is true of two subspecies of B. terrestrisB. terrestris dalmatinus and B. terrestris audax

Limitations on foraging precision
While bees are highly adept at discrimination tasks, they are still limited by the magnitude of difference needed in hue to properly carry out these tests. Error rates of color recognition decrease in B. terrestris when flower pigments are closer together on the color spectrum. This might have damaging effects on pollination efficiency if bees visit different flower species with similar, but distinct colors, which can only be mediated if the flowers have unique shapes.

Social learning
While bees often forage alone, experiments demonstrate that young foragers might learn what flowers provide the most nectar more quickly when foraging with older workers. B. terrestrisindividuals have a faster learning curve for visiting unfamiliar, yet rewarding flowers, when they can see a conspecific foraging on the same species. The discovery of this type of associative learning is a novel insight into bee behavior and may supplement learning via color reward association.

[Image: Buff-tailed-bumble-bee-with-well-filled-...tutsan.jpg]

Parasites and disease
Brood parasites

B. terrestris is parasitized by B. bohemicus, a brood-parasitic Cuckoo bee that invades B. terrestris hives and takes over reproductive dominance from the host queen, laying its own eggs that will be cared for by host workers. Another brood parasite is the bee B. vestalis. Both of these are distributed in various regions of Europe. The difference between B. bohemicus and B. vestalis is that the former parasitizes several bumble bee species while B. vestalis exclusively parasitizes B. terrestris.

Effects of foraging on resistance
Foraging is considered energetically costly and it is possible that individuals that spend more time foraging suffer costs to their overall fitness. For example, B. terrestris is often vulnerable to parasitism by conopid flies in Central Europe, and it has been hypothesized that foragers might suffer higher incidences of parasites due to the increased metabolic costs of flying. This was demonstrated in a population in which foraging workers had significantly lower levels of encapsulation of an experimental parasitic egg when compared to non-foraging workers. This suggests that foragers have compromised immune systems due to increased energetic expenses and might be predisposed to fly parasites.

Effects of polyandry on resistance
While B. terrestris is a singly mating species, a polyandrous system would potentially be beneficial because it would be possible to attain greater genetic variability for resistance against disease. Accordingly, artificially increasing the number of mates a B. terrestris queen obtains through artificial insemination has shown that the increased genetic variability in her offspring confers greater resistance to the most common bumblebee parasite, Crithidia bombi. However, the average reproductive success between one and multiple matings is not linear. Queens that mated once and mated four times had a higher fitness than those that mated twice. This suggests that there might be a fitness barrier to increased matings, which might be why colonies are usually monandrous.

Surprisingly, the immunocompetence, as measured by the ability to encapsulate a novel antigen, does not vary based on the local environment. Experimental studies demonstrate that B. terrestrishave equal levels of encapsulation in poor and stable environments. This is unexpected, because immunity should be compromised in conditions where food supply is low in order to save energy. Perhaps encapsulation represents an invariable trait of bumblebees, or immunity is far too complex to characterize solely based on measurements of encapsulation.

Threats from disease
Deformed wing virus (DMV) is normally a honey bee pathogen that results in reduced and crumpled wings, making those individuals inviable. This virus is thought to have spread to B. terrestris, and in 2004, as many as 10% of queen bees bred commercially in Europe were found dead with deformed wings. This was confirmed as DMV when B. terrestris colonies tested positive for the presence of DMV RNA. This could indicate that DMV is a broad range pathogen among bees, or perhaps it has recently been infecting new hosts after transmission from honey bees.

[Image: Buff-tailed-bumblebee-in-flight-with-ful...askets.jpg]

Environmental concerns
Invasive species

While native to Europe, B. terrestris has been introduced as a greenhouse pollinator into many foreign ecosystems. The presence of B. terrestris is becoming an ecological concern in many communities in which it is not native. It is classified as an "invasive alien species" in Japan. For example, B. terrestris has a large niche overlap with local Japanese bee species in terms of flower resources and nest sites. B. terrestris queens competing for local underground nest sites are displacing B. hypocrita sapporoensis. However, B. pseudobaicalensis, which visits similar flowers but only forms nests above ground, has not seen a rapid decline in population numbers.

In 2008, the Australian government banned the live import of B. terrestris into Australia on the grounds that it would present a significant risk of becoming a feral species and thereby present a threat to native fauna and flora. In 2004, this bumblebee was classified as a 'Key Threatening Process' by the Scientific Committee of the New South Wales Department of Environment.

This species was introduced to Chile in 1998. It has since crossed into Argentina, and is spreading at about 275 km per year. Its spread has been detrimental to populations of Bombus dahlbomii, which is the only bumblebee species native to southern South America (Patagonia, Southern Chile and Argentina). Bombus terrestris populations facilitated such massive and immediate population decline of Bombus dahlbomii through competition and pathogen introduction/spillover. Bombus ruderatus, a bee previously introduced in 1982, is also seriously affected. The cause is thought to be the parasite Apicystis bombi, an organism carried by the buff-tails, but which has no adverse effect on that species.

Colony development in changing environments
In temperate areas, variable climates and environmental conditions occur during changing seasons. Lack of available food due to these unpredictable circumstances can often negatively affect colony growth, reproduction, and resistance to parasites. In poor environments with limited food, the few workers born are smaller than average. However, it appears that B. terrestris is well adapted to a changing environment, considering colony growth is higher under variable feeding conditions than under stable feeding conditions. Workers and reproductives are also heavier with a variable food supply when compared to stable food availability. This might indicate an adaptive strategy of increased provisioning to save for days it is hard to find food.

Pesticide exposure
In their 2014 study published in Functional Ecology researchers using Radio-Frequency Identification (RFID) tagging technology on the bees, found that a sublethal exposure to either a neonicotinoid (imidacloprid) and/or a pyrethroid (?-cyhalothrin) over a four-week period caused an impairment of the bumblebee's ability to forage. Research published in 2015 showed that bees prefer solutions containing neonicotinoids, even though the consumption of these pesticides caused them to eat less food overall. This work implies that treating flowering crops with such pesticides presents a sizeable hazard to foraging bees.

Human importance
Commercial use

Since 1987, B. terrestris has been bred commercially for use as a pollinator in European greenhouse crops, particularly tomatoes—a task which was previously carried out by human hand. B. terrestris has been commercially reared in New Zealand since the early 1990s, and is now used in at least North Africa, Japan, Korea, and Russia, with the global trade in bumblebee colonies probably exceeding 1 million nests per year. In Korea, however, some have chosen Bombus ignitus over the already established commercial pollinator, Bombus terrestris, for fear of competition or genetic contamination by mating with native bumblebee species. Also, there has been a ban on importing B. terrestris into North America which resulted in higher interest in other species like B. impatiens in North America.

Nonetheless, B. terrestris are key commercial pollinators in Europe, which has driven researchers to investigate the influence of agricultural land on the foraging and survival of this species. Monoculture reduces biodiversity in farmland areas, and likely decreases the number of flowering species bees can forage on. B. terrestris consequently exhibits greater nest growth in suburban areas than in farmland, because local suburban gardens promote more plant diversity for bees to feed from. Agriculture has a profound impact on many bumblebees, and is causing widespread decline in several species. However, B. terrestris is still widespread, likely because it can forage at very long distances, making it less sensitive to changes in biodiversity and the environment.

Male bees have more than a one-track mind

Date: November 13, 2015
Source: Queen Mary, University of London
Male bumblebees are believed to have few aptitudes beyond mating and thought to be not just lazy but simple. In comparison, for example, worker bees are well known to learn the location of their hive, the colors and scents of rewarding flowers. However, male bumblebees are just as smart as female worker bees despite their dim-witted reputation, according to new research.

[Image: 151113050935_1_900x600.jpg]
Male bumblebees -- once thought to be good for just sex -- are actually just as smart as female worker bees.
Credit: Queen Mary University of London (QMUL)

Male bumblebees are just as smart as female worker bees despite their dim-witted reputation, according to new research from Queen Mary University of London (QMUL).

Researchers from QMUL's School of Biological and Chemical Sciences trained male and female bumblebees to distinguish between artificial flowers that contained food and another that did not.

The new study published in the journal Animal Behaviour found male bumblebees equal the female or worker bee's excellence in learning which flowers reward with food.

Roles within a bee colony are tightly regulated with the sterile female (also known as worker) bees performing all the labour such as, cleaning the hive, defending the colony, collecting and storing food, and feeding the young. Male bumblebees are believed to have few aptitudes beyond mating and thought to be not just lazy but simple. In comparison, for example, worker bees are well known to learn the location of their hive, the colours and scents of rewarding flowers.

Dr Stephan Wolf, lead author of the research, said: "Despite fundamental differences in the daily habits between male and female bees, this work illustrates that male bees can be clever shoppers in the flower supermarket even when their main interest is in mating."

The study tested the bees' ability to associate the flower colour with the reward of food. Flower colours where changed after some time, and bees had to forget the previously learned cue and learn a new colour as indicator for nectar or food. Over four sequential colour changes, the researchers demonstrated that male and worker bees are equally good at learning floral colours to guide them to those flower types that provide them with nectar even when the colours of the rewarding flowers will change over time.

Professor Lars Chittka, co-author of the study, suggests that: "Since bumblebee males can't sting, they are a useful model to study insect learning behaviour without the constant risk of painful encounters."

Story Source: Queen Mary, University of London. "Male bees have more than a one-track mind." ScienceDaily. (accessed November 14, 2015).

Journal Reference:
Stephan Wolf, Lars Chittka. Male bumblebees, Bombus terrestris, perform equally well as workers in a serial colour-learning task. Animal Behaviour, 2016; 111: 147 DOI: 10.1016/j.anbehav.2015.10.009

• Bumblebee males are highly efficient in associating colour cues with sucrose reward.
• Males and workers (females) are similar in learning ability of novel rewarding cues.
• Learning performance is determined by the feeder colours but not by sex.
• Sex-specific behavioural repertoire does not affect foraging cognitive abilities.
• Male bumblebees are an advantageous model system to study pollinator cognition.
The learning capacities of males and females may differ with sex-specific behavioural requirements. Bumblebees provide a useful model system to explore how different lifestyles are reflected in learning abilities, because their (female but sterile) workers and males engage in fundamentally different behaviour routines. Bumblebee males, like workers, embark on active flower foraging but in contrast to workers they have to trade off their feeding with mate search, potentially affecting their abilities to learn and utilize floral cues efficiently during foraging. We used a serial colour-learning task with freely flying males and workers to compare their ability to flexibly learn visual floral cues with reward in a foraging scenario that changed over time. Male bumblebees did not differ from workers in both their learning speed and their ability to overcome previously acquired associations, when these ceased to predict reward. In all foraging tasks we found a significant improvement in choice accuracy in both sexes over the course of the training. In both sexes, the characteristics of the foraging performance depended largely on the colour difference of the two presented feeder types. Large colour distances entailed fast and reliable learning of the rewarding feeders whereas choice accuracy on highly similar colours improved significantly more slowly. Conversely, switching from a learned feeder type to a novel one was fastest for similar feeder colours and slow for highly different ones. Overall, we show that behavioural sex dimorphism in bumblebees did not affect their learning abilities beyond the mating context. We discuss the possible drivers and limitations shaping the foraging abilities of males and workers and implications for pollination ecology. We also suggest stingless male bumblebees as an advantageous alternative model system for the study of pollinator cognition. 
[Image: wildcat10-CougarHuntingDeer.jpg]
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  • Claudiu Constantin Nicolaescu
Oxalaia Wrote:Bombus terrestris subspecies

Ssp. terrestris
Range: Continental Europe north of 45th parallel, Scandinavia

Ssp. audax
Range: British islands

Ssp. xanthopus
Range: Corsica, hybridizes with ssp. dalmatinus on Elba and Capraia island.

Ssp. sassaricus

Range: Sardinia

Ssp: lusitanicus
Range: Iberian peninsula, SW France, Balearic islands, Madeira.

Ssp. africanus
Range: North Africa

Ssp. calabricus
Range: South Italy, Sicily

Ssp. canariensis
Range: Canary islands

Ssp. dalmatinus
Range: SE France, North Italy, Balkan peninsula and surrounding regions, Turkey, Caucasus, North Iran, Alai, Altai

Note: Coppée et al. 2010 considered the ssp. africanus, canariensis, xanthopus and sassaricus as good species.
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  • Claudiu Constantin Nicolaescu
Radar tracking reveals the 'life stories' of bumblebees as they forage for food

Date: August 4, 2016
Source: Queen Mary University of London

[Image: 160804152719_1_900x600.jpg]
A bumblebee forager fitted with a lightweight transponder which allows researchers to track its position is seen sitting on a dead thistle.
Credit: Joseph Woodgate

Scientists have tracked the flight paths of a group of bumblebees throughout their entire lives to find out how they explore their environment and search for food.

This is believed to be the first time any insect has been tracked throughout its whole life.

In this unconventional study, the researchers from Queen Mary University of London (QMUL) discovered the individual bumblebees differed greatly from one another in the way they flew around the landscape when foraging for nectar.

It was also revealed the bees combined exploration of their environment with making the most of food sources they had already discovered.

Bees provide an invaluable service to both natural and agricultural ecosystems by pollinating flowers. Understanding how they use the space available to them, and how and when they find food, will provide valuable insights into how to manage landscapes to benefit plants, insects and agricultural crops.

Dr Joseph Woodgate, of the School of Biological and Chemical Sciences at QMUL, said: "This study provided an unprecedented look at where the bees flew, how their behaviour changed as they gained experience and how they balanced the need to explore their surroundings - looking for good patches of flowers - with the desire to collect as much food as possible from the places they had already discovered."

The bees were tracked using harmonic radar technology and a small, light-weight piece of electronic equipment which was attached to each one. In total, 244 flights made by four bees were recorded, encompassing more than 15,000 minutes and covering a total distance of more than 180km.

Professor Lars Chittka, coordinator of the study, said: "For the first time, we have been able to record the complete 'life story' of a bee. From the first time she saw the light of day, entirely naive to the world around her, to being a seasoned veteran forager in an environment full of sweet nectar rewards and dangerous threats, to her likely death at the hands of predators, or getting lost because she has ventured too far from her native nest."

Dr James Makinson, who is joint-first-author with Dr Woodgate, added: "One bee was something of a lifelong vagabond, never settling down on a single patch of flowers. In contrast another of our bees was exceptionally diligent, quickly switching after only three flights from exploration of the surrounding environment to focusing exclusively on a single forage location for six consecutive days.

"After six days this bee switched her attention to a closer forage source. She was able to do this without re-exploring her environment, suggesting she had remembered the location from her initial explorations. Our other two bees interspersed foraging for a single location with exploratory flights throughout their entire life."

The researchers identified two categories of flight - exploration and exploitation flights. Exploitation of memorised food sources takes place during efficient trips usually to a single foraging location. This is rarely combined with the exploration of unfamiliar areas.

Meanwhile, exploration of the landscape typically occurs in the first few flights made by each bee and this is when bees discover most of the places they will return to for feeding during their lives, although further exploration flights are sometimes made.

The results could help us understand how to manage crops so as to maximise the free pollination services provided by wild bees as well as how to manage conservation efforts to allow wild bee populations to flourish. The study could also help to explain the way the genes of bee-pollinated plants spread throughout the landscape and shed light on the way parasites and diseases can be spread between patches of plants.

The paper, titled 'Life-long radar tracking of bumblebees', was produced in collaboration with Rothamsted Research and was published in the PLOS ONE journal.

Story Source: Queen Mary University of London. "Radar tracking reveals the 'life stories' of bumblebees as they forage for food." ScienceDaily. (accessed August 5, 2016).

Journal Reference:
Joseph L. Woodgate, James C. Makinson, Ka S. Lim, Andrew M. Reynolds, Lars Chittka. Life-Long Radar Tracking of Bumblebees. PLOS ONE, 2016; 11 (8): e0160333 DOI: 10.1371/journal.pone.0160333

Insect pollinators such as bumblebees play a vital role in many ecosystems, so it is important to understand their foraging movements on a landscape scale. We used harmonic radar to record the natural foraging behaviour of Bombus terrestris audax workers over their entire foraging career. Every flight ever made outside the nest by four foragers was recorded. Our data reveal where the bees flew and how their behaviour changed with experience, at an unprecedented level of detail. We identified how each bee’s flights fit into two categories—which we named exploration and exploitation flights—examining the differences between the two types of flight and how their occurrence changed over the course of the bees’ foraging careers. Exploitation of learned resources takes place during efficient, straight trips, usually to a single foraging location, and is seldom combined with exploration of other areas. Exploration of the landscape typically occurs in the first few flights made by each bee, but our data show that further exploration flights can be made throughout the bee’s foraging career. Bees showed striking levels of variation in how they explored their environment, their fidelity to particular patches, ratio of exploration to exploitation, duration and frequency of their foraging bouts. One bee developed a straight route to a forage patch within four flights and followed this route exclusively for six days before abandoning it entirely for a closer location; this second location had not been visited since her first exploratory flight nine days prior. Another bee made only rare exploitation flights and continued to explore widely throughout its life; two other bees showed more frequent switches between exploration and exploitation. Our data shed light on the way bumblebees balance exploration of the environment with exploitation of resources and reveal extreme levels of variation between individuals.

Attached to this post:[Image: attach.png] Life_Long_Radar_Tracking_of_Bumblebees.pdf (3.68 MB)
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  • Claudiu Constantin Nicolaescu
Beware of sleeping queens underfoot this spring

March 20, 2019, Queen Mary, University of London

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Queen bumblebee Credit: Joe Woodgate

Scientists at Queen Mary University of London have discovered a never before reported behaviour of queen bumblebees.

It was long thought that queen bumblebees, after hibernating in the ground over winter, emerged, began feeding and dispersed quite quickly to found their new colony.

But new research shows that directly after hibernation, queen bumblebees spend the majority of their time hiding and resting amongst dead leaves and grass.

The study, published in the journal Scientific Reports, suggests that this behaviour of long rests with short intermittent flights explains how queen bumblebees find themselves far away from their natal nest.

Dr. James Makinson, who co-led the study at Queen Mary University of London but is now based at Hawkesbury Institute for the Environment at Western Sydney University, said: "We wanted to see what queens actually do right after they emerge. By combining state-of-the-art tracking technology with wild bee observations, we were able to uncover a never before seen behavior of queen bumblebees."

The researchers placed small antenna on the backs of queens that had just emerged from artificially induced hibernation. At an outdoor field site, radar was used to track the bees via the antennae as they woke up and left the area.

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Queen bumblebee with antenna Credit: James Makinson

The data showed that the queens were spending most of their time on the ground (between 10-20 minutes on average) and making short flights (10-20 seconds on average) in nearly random directions. Observations of wild queen bumblebees verified this was not due to the antennas but rather natural behaviour of recently emerged queens. Computer modelling also showed that this behaviour can explain how bees end up many kilometres from the hibernation spots.

Dr. Joe Woodgate, a co-lead author of the study from Queen Mary University of London, said: "Our study suggests that a few weeks of this type of behaviour would carry queen bees several kilometers away from their hibernation site and might explain how queens disperse from the nest in which they were born to the place they choose to found a new colony."

Dr. Makinson added: "Better understanding the behavior of queens during this crucial period of their lives can suggest practices to improve their chances of successfully founding new colonies and help their survival.

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Queen bumblebee resting among leaves Credit: Clint Perry

"Our findings suggest that creating pollinator friendly corridors between conserved landscape patches would be helpful. It would also be beneficial to plant pollinator friendly flowers and trees all year round, giving bumblebee queens ample access to food during their early spring emergence. And leaving vegetation, such as leaf litter and long grass, undisturbed until late in the spring would give queen bumblebees safe places to rest."

If you see an exhausted bumblebee queen around this time of the year, researchers suggest you can rescue her by giving her sugar solution (half water, half sugar, thoroughly stirred). Put the solution on a teaspoon and move the spoon gently to near her antennae or mouthparts. Drinking the solution will allow the bee to warm up its flight motor and have sufficient energy to find flowers on its own.

Journal Reference:
 James C. Makinson, Joseph L. Woodgate, Andy Reynolds, Elizabeth A. Capaldi, Clint J. Perry, Lars Chittka. "Harmonic radar tracking reveals random dispersal pattern of bumblebee (Bombus terrestris) queens after hibernation'. Scientific Reports. DOI: 10.1038/s41598-019-40355-6

The dispersal of animals from their birth place has profound effects on the immediate survival and longer-term persistence of populations. Molecular studies have estimated that bumblebee colonies can be established many kilometers from their queens’ natal nest site. However, little is known about when and how queens disperse during their lifespan. One possible life stage when dispersal may occur, is directly after emerging from hibernation. Here, harmonic radar tracking of artificially over-wintered Bombus terrestris queens shows that they spend most of their time resting on the ground with intermittent very short flights (duration and distance). We corroborate these behaviors with observations of wild queen bees, which show similar prolonged resting periods between short flights, indicating that the behavior of our radar-monitored bees was not due to the attachment of transponders nor an artifact of the bees being commercially reared. Radar-monitored flights were not continuously directed away from the origin, suggesting that bees were not intentionally trying to disperse from their artificial emergence site. Flights did not loop back to the origin suggesting bees were not trying to remember or get back to the original release site. Most individuals dispersed from the range of the harmonic radar within less than two days and did not return. Flight directions were not different from a uniform distribution and flight lengths followed an exponential distribution, both suggesting random dispersal. A random walk model based on our observed data estimates a positive net dispersal from the origin over many flights, indicating a biased random dispersal, and estimates the net displacement of queens to be within the range of those estimated in genetic studies. We suggest that a distinct post-hibernation life history stage consisting mostly of rest with intermittent short flights and infrequent foraging fulfils the dual purpose of ovary development and dispersal prior to nest searching.
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