Large Garden Bumblebee

Appearance

The body lengths of "B. ruderatus" reach about 22 mm in queens, 16 mm in workers and 15 mm in males. It has a long face and tongue, which is well adapted for feeding on long-tubed flowers. The basic color of the body is black with two yellow bands on its mesonoma—one on its scutellum and one on its pronotum—and a single thin yellow band on the abdomen. A black band is located on the interwing and separates the two yellow bands on the thorax. Similarly, queens are the most difficult to find as the bee is scarce in many areas and queens are less abundant within a colony itself.

Distribution

"Bombus ruderatus" is naturally found in Europe and north Africa, favoring large flower-rich areas of meadowland that support numerous species of plants with long-corolla flowers. It is vital that pollen and nectar sources are available within foraging distance of nests from April to September. Specifically in Europe, this species is present in Austria, Belgium, Great Britain, the Czech Republic, Denmark, France, Germany, Italy, Poland, Romania, Spain, and Switzerland. Since the 1800s it has been used commercially in non-native countries to assist with crop pollination. In 1885, "B. ruderatus" was introduced into New Zealand to pollinate the red clover plant, and in 1982, it was introduced into Chile for the same purpose. Since 1993, this species has also been seen in Argentina’s Patagonia, thought to have traveled there through the low-altitude sections of the Andes. Many parts of the world, including western Europe and North America, have seen declining populations of their native bumblebees due to many contributing factors. In Britain specifically, habitat fragmentation has led to declines in "B. ruderatus", in both population size and pollination range. "B. ruderatus" is commonly found in sympatric distribution with "B. hortorum", but the latter has seemed to be unaffected by fragmentation, since it is still relatively commonly in Britain. Conversely, "B. ruderatus" has become one of the most rare of the 23 English bumblebees.In recent years, many countries have seen decreases in bee populations, specifically bumblebees. Some possible explanations could include habitat fragmentation, climate change, disease, agrochemicals, and other factors. As stated previously, "B. ruderatus" has seen a population decline in Britain and has disappeared completely from many of its previous sites. Declines in bee populations can lead to other ecological issues, such as declines in the success of plant species that rely on their pollination.Recently, the European Union has introduced agri-environment plans that can be used to pay farmers to manage their land in a way that benefits bee species. Britain adopted the Environmental Stewardship scheme with the goal of enhancing the supply of pollen and nectar sources for bumblebees. These plans hope to counteract some of the issues that commercial developments have caused. For example, intense crop management with decreased mixed farming has led to “botanical simplification” of habitats, which may have contributed to decreased bumblebee populations by decreasing the quality and quantity of resources and habitats.

Reproduction

Most "Bombus ruderatus" nests tend to be subterranean. Queens have been seen to return to their maternal nest site, but will assess it indiscriminately to determine if it is suitable for colonization.In "Bombus ruderatus", worker oviposition has been seen in association with oophagy, which may include the queen eating eggs deposited by workers. Larvae ejection was also a common process done by workers and sometimes queens, and involved pulling live larvae out of cells and depositing them outside of the nest. Analysis of ejected and survivor larvae showed no morphological difference so the reason for ejection is unknown, but female ejection occurred more frequently than male ejection.

Food

In Argentina, "Bombus ruderatus" is most commonly found feeding from plant species from families Fabaceae, Alstroemeriaceae, and Rosaceae. Newly emergent queens tend to consume more pollen than the much smaller males.