The sting Bumblebees can sting, at least the queens and workers can, and their sting is not barbed like that of the honeybee, so they can sting more than once. The photograph on the left shows the sting of a Bombus lapidarius queen. I found her dead in the garden one morning. It was early in the season so she may have been fighting over a nest site with another queen, or she may just have died in the cold of the night. I have never been stung, but I have heard that a bumblebee sting is less painful than a wasp sting, some say it is also less painful than a honey bee sting, others that it is more painful.
Bumblebees seem reluctant to sting, and appear to do so only if they feel really threatened .
So I feel that it is best to treat bumblebees with respect as there are some people who have an allergy to bee venom that can lead to death even after just a single sting if not treated promptly. On the right of the picture you can just see the two claws at the end of her middle leg. Well the hairs do provide some insulation, but to raise their temperature for flight they simply uncouple their wing muscles so that the wings themselves do not move but use the muscles to shiver and raise their thorax temperature. So when their thorax is warm enough they can fly. This is why you may find some grounded bumblebees in cold spells in the spring.