Bumblebees are a diverse group of over 250 social insect species, important pollinators for wild plants and agricultural crops. Their global presence, specific habitats, and ecological factors shape their distribution.
Worldwide Presence
Bumblebees are primarily found across the Northern Hemisphere, spanning Europe, Asia, and North America. They are also present in parts of South America, including lowland tropical species and the Patagonian bumblebee in Chile and Argentina. European bumblebees have been introduced to New Zealand and Tasmania.
Bumblebees thrive in temperate climates, often at higher latitudes and altitudes than other bee species. For instance, Bombus polaris is found in extremely cold environments like northern Ellesmere Island in the high Arctic, marking the northernmost occurrence of any eusocial insect. Conversely, bumblebees are largely absent from most of Sub-Saharan Africa, Australia, and Antarctica.
Specific Environments
Bumblebees inhabit a variety of environments, including prairies, meadows, mountainous regions, savannas, agricultural landscapes, and wetlands. They also adapt to urban areas, colonizing gardens and parks where flowering plants are available.
Suitable environments depend on abundant flowering plants and nesting opportunities. Bumblebees commonly nest underground in abandoned rodent burrows, compost heaps, or sheltered spaces under sheds. Other species prefer above-ground sites like dense grass tussocks, mossy vegetation, tree holes, or cavities in structures. Unlike some other bees, bumblebees do not excavate their own nests; they occupy pre-existing cavities.
Ecological Factors Shaping Their Home
Bumblebee distribution is influenced by ecological factors, particularly their ability to regulate body temperature. Adapted to cooler climates, bumblebees generate heat to warm flight muscles (30-40°C) even in low ambient temperatures. They do this by rapidly vibrating flight muscles, similar to shivering. Their fuzzy, insulatory bodies help retain this warmth.
When temperatures rise, bumblebees shunt excess heat from their thorax to their abdomen for dissipation. Worker bees maintain a stable nest temperature for their brood, ranging from 30 to 33 degrees Celsius. Despite these abilities, extreme heat, especially above 35 degrees Celsius, can negatively impact larvae and pupae.
Continuous availability of diverse floral resources is another factor for bumblebee survival. Colonies require nectar for energy and pollen for protein from early spring through late fall. While generalist pollinators, individual species may prefer blue, purple, pink, and yellow blooms. Varied flowering plants with overlapping bloom periods ensure a consistent food supply throughout their active season.
Suitable nesting sites also determine bumblebee presence. Queens seek sheltered, insulated locations. Abandoned rodent burrows are often chosen for their protective structure and insulation. Other options include dense grass clumps, compost piles, and various natural or man-made cavities. While a colony comprises 50 to 400 individuals and lasts only a few months, new queens hibernate in separate, often underground, sites before starting new colonies in spring.