9-6-2015 MONTE CORONA, VALENCIA - BUFF TAILED BUMBLE BEE (Bombus terrestris)

Bombus terrestris, the buff-tailed bumblebee or large earth bumblebee, is one of the most numerous bumblebee species in Europe. It is one of the main species used in greenhouse pollination, and so can be found in many countries and areas where it is not native, such as Tasmania. Moreover, it is a eusocial insect with an overlap of generations, a division of labour, and cooperative brood care. The queen is monogamous which means she mates with only one male. B. terrestris workers learn flower colours and forage efficiently.

B. terrestris are pollen-storing bees that generally feed and forage on nectar and pollen. The queen is between 20 and 22 mm long, males range from 14 to 16 mm, and workers from 11 to 17 mm. Workers have 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 as in the workers in B. lucorum. B. terrestris is 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.

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, it has escaped captivity after being introduced as a greenhouse pollinator in countries where it is not native, so this bee is now considered an invasive species in many of these places, 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 lay egg cells on top of one another. Colonies produce between 300 and 400 bees on average, with a large variation in the number of workers.

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. There is only one per 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. Mating is their sole role in the colony.