Bumblebees are social insects that are characterised by black and yellow body hairs, often in bands. However, some species have orange or red on their bodies, or may be entirely black.[2] Another obvious (but not unique) characteristic is the soft nature of the hair (long, branched setae), called pile, that covers their entire body, making them appear and feel fuzzy. They are best distinguished from similarly large, fuzzy bees by the form of the female hind leg, which is modified to form a corbicula: a shiny concave surface that is bare, but surrounded by a fringe of hairs used to transport pollen (in similar bees, the hind leg is completely hairy, and pollen grains are wedged into the hairs for transport).
Like their relatives the honey bees, bumblebees feed on nectar and gather pollen to feed their young.The blood or hemolymph, as in other arthropods, is carried in an open circulatory system.[3] The body organs, "heart" (dorsal aorta), muscles, etc. are surrounded in a reservoir of blood, and pulsing contractions of the tube-like dorsal aorta create a weak circulatory force.
In fertilised queens the ovaries are activated when the queen lays her egg. It passes along the oviduct to the vagina. In the vagina there is a chamber called the spermatheca. This is where the queen stores sperm from her mating. The queen, depending on need, may allow her egg to be fertilised. Non-fertilised eggs become males, and only fertilised eggs grow into females and queens.
As in all animals, hormones play a significant role in the growth and development of the bumblebee. The hormones that stimulate the development of the ovaries are suppressed in female worker bees, while the queen remains dominant.