Well it depends what it is doing. Very slowly when the queen is looking for a nest site, and also when flying low over flowers. However when a worker emerges from the nest to fly to a known foraging site she can fly much faster than I could run when I was reasonably fit. Some foraging bumblebees have been recorded flying at 16 km per hour.
As mentioned in the life cycle page, the males emerge from the nest before the queens. When the males are not drinking nectar from flowers they fly along regular routes stopping on the way. Studies in Scandinavia have shown that each species has a favoured height for these patrols, some fairly close to the ground, and others at around 15 metres. They stop at the same places on route, there are probably easily seen landmarks, and deposit a fragrant secretion from a gland between their mandibles (jaws). This tends to happen in the morning, but they will replenish the marking after rain. Again the group of chemicals that make up the secretion appears to be different in each species. Sladen, in his book, says that this secretion has a smell that even humans could detect, and that it is very pleasant. It is not known for sure, but it is assumed that the queens detect the males by flying around at the correct height till they detect the fragrance of the males. Then mating takes place. However mating is rarely observed in the wild. The bees couple with the male hanging on to the queens back. Usually they mate on the ground or foliage, but there have been sightings of largish queens flying with a small male still attached to her. The time taken for matings also varies widely from 10 to 80 minutes. However the time taken fro the transfer of sperm from the male to the queen is only 2 minutes. The rest of the time is taken up with waiting for the sticky genital plug passed from the male to the queen to harden inside the queen's genital opening. This plug prevents the passage of sperm from other matings, so this may be the reason that the bees stay stuck together in a very vulnerable position, and may explain sightings of large queens flying around with hapless males stuck behind them. Perhaps she just got fed up once the necessary (for her anyway) bit was over.
There are many, but the big three are:
Some bumblebees have a whitish or yellow patch of hairs just below or between their eyes. In the European species and, I believe, in some American species these are males. They cannot sting, and generally they appear towards the end of the nest life, just before the new queens hatch out.
No. The bumblebee's jaws are just not strong enough. They cannot bite or gnaw through wood either.
The buzzing sound is heard when the bee makes the air vibrate in some way. It used to be thought that the movement of the wings caused the sound. However the bees can buzz even when the wings are at rest. So it is probably the vibration of the muscles in the thorax causing the thorax to vibrate that makes the buzzing sound.
Human engineers with big brains said it was impossible for bumblebees to fly. But bumblebees with small brains didn't know this so continued to fly on in blissful ignorance. For more background on this story of our ignorance and arrogance read these links. Link 1, Link 2, Link 3
Actually it can do both, but it mandibles (jaws) are not strong enough to cause any pain to a human, and are used mainly for moulding the wax for the cocoons, honeypots and pollen stores. Also the mandibles are rounded, so have next to no piercing ability. Some species, mainly Bombus lucorum, do use their mandibles for nectar robbing, but it takes them ages to pierce through a flower to steal the nectar, so human skin is in no danger. This is also why a bumblebee nest in the house will cause no damage as they cannot drill or dig. Workers (females) and queens can sting (see this page for photographs etc.), and they have an unbarbed sting , so could sting repeatedly,unlike honey bees, but rarely do. The only time I have heard of bumblebees stinging is when they have been roughly handled, or their nest or the entrance to the nest is being tampered with. I have never been stung, and I have handled hundreds, measuring tongue lengths, head widths etc. I can honestly say they are the most accommodating insects to work with - hence my deep fondness for them.
No. Bumblebees, like all other insects, have what is called an exoskeleton. This simply means that the skeleton is on the outside of the body, unlike our skeleton which is on the inside. The skeleton of the main part of the body is made up of hard plates of chitin held together by more flexible thinner sections of chitin. This allows for some expansion and movement, but not much real growth. This is why, during the larval stage, the insect has to moult to grow bigger. And once the insect has emerged as an adult that is as big as it gets.