The tree bumblebee or new garden bumblebee (Bombus hypnorum) is a species of bumblebee common in the European continent and parts of Asia. Since the start of the twenty-first century, it has spread to the United Kingdom and Iceland.
- 1 Description
- 2 Taxonomy and Phylogeny
- 3 Distribution
- 4 Habitat
- 5 Colony Cycle
- 6 Breeding
- 7 Behaviour
- 8 Life History
- 9 Interactions
- 10 References
- 11 External links
Bombus hypnorum has a short proboscis and a rounded head. The thorax is usually of a uniformly ginger colour (but examples with a darker, or even black thorax occur), the abdomen is black-haired and the tail is always white. In workers, the first tergite (abdominal segment) is black-haired, but a proportion of males may have ginger hairs intermixed with the black hair, both on the face and on the first abdominal tergum. On the European continent, individuals with extended yellow coloration exist. Workers are often (but not always) small, while drones are much bigger in comparison. The queens vary in size. 
Taxonomy and Phylogeny
B. hypnorum is a common bumblebee species in continental Europe and northern Asia, from northern France to Kamchatka in the east, and from the Pyrenees to the mountains in northern Europe. It is not found, though, in the Mediterranean, the Balkans, or the steppes of eastern Europe, only in the mountains of the Iberian Peninsula and not south of Tuscany in Italy. The bumblebee was first observed in United Kingdom on 17 July 2001 close to the village of Landford in Wiltshire, and has since been spreading widely. In August 2008, B. hypnorum was found in Iceland, and queens have been found each year since. It likely will continue to stay in Iceland and prosper in close living with humans near dense settlements, i.e. Reykjavík, but will most likely not venture into the more rural parts of Iceland. It has now moved from England up to part of Scotland and Wales in the UK. It also is distributed around Europe and Asia.
The bumblebee often lives near human settlements. It prefers to build its nest above ground and often inhabits bird boxes. B. hypnorum likes to live in forests but in places where they are not as many trees, they also favors human dwellings. They like to live in holes and walls in the trees unlike other members of the Bombus species. They do not stay in areas where there is a high amount of oilseed rape cover. Since they live in areas different from other Bombus species, they eventually can pollinate areas that others do not. 
The nest is quite large, with 150 workers or more (according to some authorities up to 400). The species is a pollen storer; it stores pollen in separate cells and feeds each larva individually, instead of storing the pollen in pockets under larval cells. It visits an enormous range of flowering plants such as Rhododendron, cherry, grape hyacinth and, in the north, Vaccinium. It is an important visitor to raspberry (Rubus idaeus) and bramble (Rubus fruticosus agg.).
The tree bumblebee has a short breeding cycle, with queens emerging early, usually in March. The first cycle is completed from mid-May to early July (depending on the season). A smaller second generation is produced in late summer in favourable years. Larger colonies have heavier queens. 
Queens in this species are polyandrous. The bees in this nest contain workers of sometimes 2 or 3 different fathers. Sometimes, there are some workers in the nest that are not genetically related to the queen and come from another nest. 
There have been dead queens around colonies that are established, so this may have been a production of one colony taking over another colony and keeping some of the workers. 
There are two parts to mating: approach and copulation. First there is the approach part where the male checks out the female. The male would approach a queen and then hover in the air for a few seconds using their antennae to inspect the female. If this male is part of the same species, then they will land and continue their inspection using their antennae. The male mounts her by using his front legs on her abdomen and mounts from the rear. Then he attempts to copulate with the female. Females have a mandibular gland that releases a pheromone that the males react to so that they will know of their receptiveness. Males use their legs to tap on the abdomen of the female for a few seconds in ten second intervals. Males of B. hypnorum copulate for about 20-40 min. 
Mating Frequency and Duration
Females in this species are unlike other species where they usually only mate once. B. hypnorum can mate 2-3 times in their lifetime; however, this is not always the case.  It has been observed that a female can mate up to 6 times. When looking at the second mating, it does not seem to be shorter or longer than the first mating, but they are usually shorter than the females that have mated only once in their lifetime. This can be due to the fact that the mating plugs disappear relatively quickly, in 6-12 hours. 
Social bees are hymenoptera. The female workers are more genetically related to each other than their brothers, so they work to increase the female ratio since they share more genes and want them to survive. 
There seems to be a hierarchy around the egg-laying workers in the nest. While the queen was alive, this bee would eat the eats of any other workers that were laying eggs in the nest. If this worker dies, the next in the hierarchy would start up this act as well and at the same time defend her own eggs.
Genetic Relatedness Within Colonies
The relatedness from sister to sister is 75% and sister to brother is 25%. This is because females are diploid and males are unfertilized haploid. The Queen has equal genetic relatedness to both her sons and daughters so she wants to lay an equal ratio of children. Since B. hypnorum also can mate with more than one male, then the colony has groups of related females.In these colonies, the queen has sex ratio control so the offspring are equally male and female. 
Development of larvae into a queen or a worker is determined by the amount of food that was given to them. Workers have a shorter development time that the queens. The Queens have a higher amount of juvenile hormone than the workers. 
The B. hypnorum’s social parasite is the B. norvegicus. B. norvegicus can produce a repellant to combat invading workers. This is very strong on B. hypnorum workers that have not had food yet. The biggest component of this repellant, dodecyl acetate, together with other chemicals, repels B. hypnorum which makes B. hypnorum take longer to get to food. This makes it harder for B. hypnorum to commit nest usurpation in their nests.
B. hypnorum has the biggest preference for the flowering trees Crateagus monogyna and Prunus spinosa compared to other types of bumble bees. Also compared to other bees, B. hypnorum has less of a preference for Brassica naptus, Glechoma hederacea and Lamium album.
Workers and males have similar responses to chemical stimuli, however the males are just slightly more responsive. Queens have the highest response overall.
The tree bumblebee is generally quite docile, but if disturbed, it can defend its nest proactively and it has been known to sting people whom it perceives as a threat.
- Benton, Ted (2006). "Chapter 9: The British Species". Bumblebees. London, UK: HarperCollins Publishers. pp. 348–350. ISBN 0007174519.
- Bumblebee conservation: Introducing the tree bumblebee by Clive Hill
- Koulianos, Stella; Schmid-Hempel, Paul (March 2000). "Phylogenetic Relationships among Bumble Bees (Bombus, Latreille) Inferred from Mitochondrial Cytochrome b and Cytochrome Oxidase I Sequences". Molecular Phylogenetics and Evolution 14 (3): 335–341.
- Pierre Rasmont. "Bombus (Pyrobombus) hypnorum (L., 1758)". Université de Mons. Retrieved 12 January 2013.
- Icelandic Ministry for the Environment News of arrival
- Icelandic Ministry for the Environment Article on Bombus hypnorum
- Crowther, Liam P.; Hein, Pierre-Louis; Bourke, Andrew F. G. (September 2014). "Habitat and Forage Associations of a Naturally Colonising Insect Pollinator, the Tree Bumblebee Bombus hypnorum". PLoS ONE 9 (9).
- Anon. "Common bumblebees:Tree bumblebee Bombus hypnorum". Bumblebee Conservation Trust. BCT. Retrieved 30 June 2013.
- Brown, M. J. F.; Schmid-Hempel, R.; Schmid-Hempel, P. (2003). "Queen-controlled sex ratios and worker reproduction in the bumble bee Bombus hypnorum, as revealed by microsatellites". Molecular Ecology 12: 1599–1605.
- Paxton, R. J.; THORÉN, P. A.; ESTOUP§, A.; TENGÖ*, J. (2001). "Queen–worker conflict over male production and the sex ratio in a facultatively polyandrous bumblebee, Bombus hypnorum: the consequences of nest usurpation". Molecular Ecology 10: 2489–2498.
- van Honk, C. G. J.; Velthius, H. H. W.; Röseler, P. F. (July 1978). "A sex pheromone from the mandibular glands in bumblebee queens". Cellular and Molecular Life Sciences 34 (7): 838-839.
- Schmid-Hempel, R.; Schmid-Hempel, P. (2000). "Female mating frequencies in Bombus spp. from Central Europe". Insectes soc. 47: 36–41.
- Brown, M.J.F.; Baer, B.; Schmid-Hempel, R.; Schmid-Hempel, P. (2002). "Dynamics of multiple-mating in the bumble bee Bombus hypnorum". Insectec Soc. 49: 315–319.
- Strambi, Alain; Strambi, Colette; Röseler, Peter-Frank; Röseler, Ingenorg (1984). "Simultaneous determination of juvenile hormone and ecdysteroid titers in the hemolymph of bumblebee prepupae (Bombus hypnorum and B. terrestris).". General and Comparative Endocrinology 55 (1): 83–88.
- Zimma, B. O.; Ayasse, M.; Tengo, J.; Ibarra, F.; Schulz, C.; Francke, W. (October 2003). "Do social parasitic bumblebees use chemical weapons? (Hymenoptera, Apidae)". J Comp Physiol A Neuroethol Sens Neural Behav Physiol. 189 (10): 769–775.
- Fonta, Caroline; Masson, Claudine (1984). "COMPARATIVE STUDY BY ELECTROPHYSIOLOGY OF OLFACTORY RESPONSES IN BUMBLEBEES (Bombus hypnorum and Bombus terrestris)". Journal of Chemical Ecology 10 (8): 1157–1168.
|Wikimedia Commons has media related to Bombus hypnorum.|
|Wikispecies has information related to: Bombus hypnorum|