Bumble bees are similar to their close relatives, the honey bees, in that their colonies are headed by a queen, who is the main egg-layer, and many workers, who are the daughters of the queen, and in that drones (males) are produced during the mating season. However, the colonies of bumble bees, unlike those of honey bees, only survive during the warm season; new queens hibernate alone to begin another colony the following spring. In addition, there are usually fewer individuals in a bumble-bee colony than in a honey-bee colony, and bumble bees do not use a dance to communicate the location of food to other members of the colony, as honey bees do. Also, although bumble bees collect nectar and store it as honey, they do not hoard large amounts of it, as do honey bees.
Because bumble bees are conspicuous and important in nature, their biology has been well studied. They are among the few insects that can control their body temperature. In cold weather, queens and workers can shiver their flight muscles to warm themselves, allowing them to fly and work at lower temperatures than most other insects. Their large size and heat-conserving hairy coats also help them stay warm. These features enable them to live in northern latitudes and alpine altitudes. Bumble bees are sensitive to habitat disturbance. In England, several species are thought to have become extinct in past decades due to land clearing and agricultural practices.
Life of the Colony
The bumble-bee nest consists of a spherical chamber with a single exit. The queen chooses a preexisting cavity, such as an abandoned mouse nest, in which to begin her family. Most species nest in the ground. The queen forms a small mound of pollen paste in the middle of the nest, lays several eggs in it, and seals it with a small dome of wax. She also constructs a hemispherical wax cup, called a honeypot, in the entranceway floor and fills it with nectar. The queen feeds on this nectar while she incubates the eggs. The newly hatched larvae partially consume the paste in their cells. Later they are fed by the queen through a small opening in the cell wall. When the larvae are fully grown, they spin cocoons in which they metamorphose, eventually emerging as the first workers of the new colony. Subsequent larvae are reared by these workers in individual cells, much as honey-bee larvae are; however, the bumble-bee nest is not organized into flat, vertical combs like that of honey bees but grows instead into a mound of capsule like cells. Toward the end of summer, the queen begins to lay unfertilized eggs that develop into drones. Female offspring produced at this time become new queens, and mating takes place soon afterward. The drones and workers then die, and the new, mated queens fly off in search of safe places to hibernate.
Some species of bumble bees, known as cuckoo bumble bees, are parasitic on the nests of nonparasitic bumble bees. They invade the nest, kill the resident queen, and force the workers to raise the young parasitic bees along with the brood of the host colony. Occasionally, the invaders permit only their own young to survive. Cuckoo bumble bees lack pollen baskets because they do not forage for pollen.
Bumble bees are important pollinators of many plants. Both queens and workers collect pollen and transport it back to the colony in pollen baskets on their hind legs. Workers are small if born early in the year, and large if born later in the year. Also, some species of bumble bees are larger than others. Differences in body size, and especially in tongue length, are important in determining which flower species a bumble bee will visit for nectar and may determine which flowers it can pollinate.
Bumble bees have long been recognized as vital to the production of certain seed crops. In recent years, bee scientists have developed a means to cause queens to skip their winter hibernation and produce colonies year-round. This has made certain species of bumble bees available for use in pollinating crops they did not before. Bumble-bee colonies are now used extensively in greenhouse pollination of crops such as tomatoes and strawberries.
Scientific classification: Bumble bees belong to the genus Bombus of the family Apidae, order Hymenoptera.
Contributed by: Evan A. Sugden