Bumblebees are relatively large flying insects in the Order Hymenoptera, Family Apidae, genus Bombus. They are usually covered with aposematically-colored pile, that is, long, branched hair in "warning" colors of black-and-yellow. Like their relatives the honey bees, bumblebees form colonies, build nests, feed on nectar, and gather pollen to feed their young.

Bumblebees usually form their nests underground, and they are much less extensive than those of honey bees. A single bumblebee queen is responsible for the initial nest construction and reproduction. Often, mature colonies will consist of fewer than 50 individuals. Bumblebees sometimes construct a wax canopy ("involucrum") over top of their nest for protection and insulation. Nests are not used year after year; the last generation of summer includes a number of queens who overwinter separately in protected spots.

Bumble bee queens that have already mated overwinter until early spring, then finds a hole or crevice in or near the ground. She builds honeypots and brood cells, and begins laying eggs. Small sterile female worker bees develop first, and begin foraging for nectar. As the weather warms into early summer, new brood cells and honeypots are constructed. These new brood cells produce larger adults which in turn are put to work gathering nectar for the colony. In autumn, fledgling queens mate with drones, and begin the cycle again.

Bumble bees differ from honey bees in many respects, not least of which is their stinger, which does not have barbs like that of the honey bee. Bumble bee stingers can be withdrawn from the victim and reused over and over again. Yow! I've been stung by honey bees many times, but never by one of these babies. They can be very intimidating, being so large and making such a loud buzz.

Bumble Bees are important pollinators of flowering plants. In this era of declining domesticated honeybee numbers, colonies of wild bumble bees take on additional importance. Bees are a crucial part of wildlife communities - known as ecosystems - because they pollinate plants in their search for their food, nectar and pollen from flowers. Worldwide, up to 40 per cent of the world's food production is due to pollination by wild bees, which include the bumblebee. Bumblebees are increasingly used in hothouse tomato production; the intense vibration produced by the flight muscles is known to efficiently dislodge the tomato flower's pollen, resulting in greater fruit production.

Many plants have evolved over the millennia to take advantage of various insects' ability to spread their pollen from plant to plant. Pollination by bees is known as melittophily.

Bee-pollinated flowers fall into two classes:
* Showy, open, bowl-shaped flowers that are relatively unspecialized (e.g. wild roses, sunflowers)
* Showy, complicated, non-radially symmetric flowers that are more specialized (e.g. peas, foxgloves)

Many bee flowers are yellow or blue, often with ultraviolet nectar guides and scent. Nectar, pollen, or both exist in varying amounts. The predominate sugar in the nectar is sucrose. Honey bees, bumble bees, orchid bees, and bees in the family Halictidae are large groups that are quite distinctive in size, tongue length and behavior (some solitary, some colonial). Thus generalization about bees is difficult (Fenster at al. 2004.) Some plants can only be pollinated by bees because their anthers release pollen internally, and it must be shaken out by buzz pollination. Bees are the only animals that perform this service.