Bee Behavior
When guard bees in a colony sense a threat, they release a volatile scent (pheromone) which functions as an alarm. Older bees, which have more venom, then defend the hive by attacking the intruder.
Smoke Purpose
Smoke decreases reactions by the guard bees so they do not send out an alarm. All the bees stay quiet, and the beekeeper can do any necessary work on the hive.
Moving a Hive
A smoker also is useful when a beehive needs to be moved. A beekeeper may be taking the hive to a different location, or a non-beekeeper might have discovered a hive on her property and wants it removed.
Smoke
Smoke is commonly created with a smoldering rag, often made of burlap because it produces reliable amounts of smoke. Dried corn cobs, corrugated cardboard and wood also can be used.
Types
Beekeepers still use very basic smokers of a style invented during the 1800s, consisting of a funnel, combustion chamber and bellows. More modern smokers also are available, with propane-fueled coils that create smoke from food-grade ingredients.