In bumblebees and other social Hymenoptera (bees, ants and wasps) fertilized eggs develop into females (queens or workers), and unfertilized eggs develop into males. For more on this see the Haplodiploidy page.
bumblebee tongue is specialised to suck up nectar (see the photograph on the right).
At rest or when flying the tongue is kept inside a sheath and folded under the
head and thorax.
Wax is secreted by glands in the abdomen and exudes between the chitinous plates of the abdomen, and looks a little like flakes of dandruff. It is scraped off by the legs and moulded into whatever is needed. The wax is used to construct honeypots, as a covering for the eggs, as a lining inside some used cocoons to make them hold nectar/honey, and sometimes as a covering for the whole nest.
Wax is secreted by the queen when she starts the nest, and by workers on the second day of adulthood. The secretions decline after a week. It is during this time that most workers spend most of their time in the nest performing household tasks. Only later do they leave the nest for the dangerous job of foraging.
A bumblebee does not have ears, and it is not known whether or how a bumblebee can hear sound waves passing through the air, however she can feel the vibrations of sounds through wood and other materials.
The heart, like that in most other insects, runs down the entire length of the body.
The fat body is a nutritional store. Before hibernation queens eat as much as they can to enlarge their fat body. The fat in the cells is used up during hibernation. The fat body is largest in queens, smaller in workers, and doesn't exist in males.
The blood (hemolymph), is not carried in veins and arteries as ours is, but just sloshes around. The body organs, heart, muscles, etc. sit in a pool of blood. The heart does pulse blood through its long tube, though, so there is a circulation of sorts.
In fertilised queens the ovaries are activated, and when the queen lays an egg it passes along the oviduct to the vagina. In the vagina there is a container called the spermatheca. This is where the queen stored sperm from her mating the previous year. Before she lays the egg she will decide whether to use sperm from the spermatheca to fertilise it or not. Non-fertilised eggs grow into male bumblebees, and only fertilised eggs grow into females and queens.
As in all animals hormones play a big role in the growth, development and behaviour of the bumblebee. The hormones that stimulate the development of the ovaries are suppressed in the other female worker bees while the queen remains dominant.
Salivary glands in the head secrete saliva which is mixed with the nectar and pollen. Saliva is also mixed into the nest materials to soften them.
It is often thought that humming birds have the highest metabolic rate of all animals, however the metabolic rate of bumblebees is 75% higher than a humming bird's!