The evolution of the sting
The sting of the bumblebee and other bees evolved from the ovipositor, that is the tube that many female insects have that the eggs passes down and they use to position the egg in a suitable place.
It is believed that the
sting evolved to be used against other insects - who do not have elastic skin - so
the sting could easily be pulled out. It is only relatively recently that
mammals have become bee predators, so the honey bee sting will probably evolve to have
smaller, then no barbs. However this does not explain the smooth bumblebee
sting, and bumblebees are usually thought as less "advanced" than honey bees.
Also it is not the survival of the individual worker that is important in a
hive or nest, but the survival of the new queens and males, as only they will
go on to breed.
What does a bumblebee sting feel like?
I have never been stung
by a bumblebee, 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. Also the pain seems to be worse in certain parts of the body - the face and neck for instance. And others complain of the swelling and irritation lasting for days after the initial pain of the sting has worn off. Bumblebees are reluctant to sting, and appear to do
so only if they are mishandled or their nest is threatened. However I have
heard recently that some species of bumblebees found in America (north and
south) are more aggressive than European species. So always 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.