Bombus terrestris, commonly known as the buff-tailed bumblebee or large earth bumblebee, is a widely recognized insect species. This social bee is among the most common bumblebee species found across its native range. It plays a role in various ecosystems, making it a subject of considerable interest in both natural environments and agricultural settings.
Identifying Bombus Terrestris
The buff-tailed bumblebee has a large, robust, hairy, black body with distinct bands. A prominent yellow or orange band forms a collar behind its head, and a second yellow band crosses the abdomen.
Its most distinguishing feature is its tail, which ranges from pure white to a deep orange-buff. This variability can lead to confusion with similar species like the white-tailed bumblebee, Bombus lucorum, which has a pure white tail. Queens are larger, measuring 20 to 22 millimeters, while males range from 14 to 16 millimeters. Workers are smaller than queens, 11 to 17 millimeters long, and their tail coloration can be paler or whiter.
Geographic Distribution and Habitat
The native range of Bombus terrestris spans Europe, North Africa, and parts of Asia, from the Canary Islands to the Altai Mountains and as far north as Helsinki. This wide distribution reflects its adaptability to various temperate climates. The species is absent from deserts, arid steppes, and high alpine levels.
Beyond its native areas, Bombus terrestris has been introduced to non-native regions like New Zealand, Tasmania, Japan, Chile, and Argentina, primarily for agricultural purposes. These introductions have led to ecological implications, as the bee can become an invasive species. In new environments, it may compete with native pollinators for floral resources and nesting sites, and can also introduce pathogens. Nests are constructed underground, often utilizing abandoned rodent burrows or other suitable subterranean cavities.
Colony Life Cycle
The life cycle of a Bombus terrestris colony follows an annual pattern, beginning with a solitary queen. After hibernating through winter, the mated queen emerges in early spring, between February and April, depending on latitude. She then searches for a suitable underground nest site, often an old mouse or vole nest.
Once established, the queen builds a small wax honey pot and lays her first batch of fertilized eggs. She broods over these eggs to keep them warm, feeding the developing larvae with nectar and pollen. After four to five weeks, the first generation of worker bees emerges. These workers take over foraging duties, collecting nectar and pollen, tending to subsequent broods, and maintaining the growing nest.
Colonies expand throughout spring and summer, reaching several hundred individuals, and over 1000 in warmer regions. In late summer, the queen begins laying unfertilized eggs, which develop into males, alongside fertilized eggs that produce new queens. These new reproductive individuals leave the nest to mate. The old queen, workers, and males then die as the colony naturally declines, leaving only the newly mated queens to find hibernation sites and repeat the cycle the following year.
Ecological and Agricultural Significance
Bombus terrestris serves as a generalist pollinator in natural ecosystems, visiting a wide variety of wildflowers. This polylectic foraging behavior means it collects nectar and pollen from hundreds of plant species. Its robust nature allows it to forage effectively even in cooler temperatures or light rain, contributing to the pollination of diverse flora.
In agriculture, Bombus terrestris is extensively used for commercial pollination, particularly in greenhouse environments. It is valued for its ability to perform “buzz pollination” (sonication), a technique where the bee vibrates its flight muscles to release pollen from flowers that hold it tightly. This method is beneficial for crops like tomatoes, peppers, eggplants, and certain berries, increasing fruit yield and quality when pollinated by these bees. While widespread and not considered threatened in its native range, like other pollinators, Bombus terrestris populations can be affected by habitat loss and the use of pesticides.