Bees are flying insects closely related to wasps and ants. There are nearly 20,000 known species of bee, in nine recognized families. They are found on every continent except Antarctica, in every habitat on the planet that contains insect-pollinated flowering plants. Although a bee sting can be deadly to those with allergies, virtually all bee species are non-aggressive if undisturbed and many cannot sting at all. In fact humans will often be a greater danger to the bees, as bees are often affected or even harmed by encounters with toxic chemicals in the environment.