Killer bees swarm over people when the bees have been only slightly disturbed, even by a person walking past their hive. They chase and will fly in pursuit for at least half a mile. They have killed 700 to 1,000 people in the Americas in the past 30 to 50 years - with anywhere from 1 to 1,500 stings at once. They have been known to have chased a pickup truck, a lawn mower and an ambulance with a sting victim inside. In the United States the death toll is still low: a South Texas man and a poodle in Arizona.
Away from the hive, however, the bees are no more aggressive than other bees or wasps. They will not form large swarms and hunt for you as suggested in movies.The bees are now advancing within the United States, having proceeded north from Brazil at the rate of 200 to 300 miles per year; they left Brazil in 1956 (thanks to the accidental release during a bee experiment of 26 queens and possibly 250 drones) and in 1990 appeared in Texas and have continued to spread there and into Arizona in 1993.
Killer bees are more formally called Africanized bees because they are a hybrid of Brazilian and Tanzanian bees. Their aggressiveness evolved in Africa, where plenty of creatures, including the honey badger, have always been after them. Africanized bees defend their nests with more vigor and in greater numbers than the common honey bee. When bees defend their colonies, they target furry and dark-colored objects that resemble their natural enemies: bears and skunks. Therefore your pets are likely to be stung when bees are disturbed.
They are even worse for American crops than for people. Many crops depend on beekeepers and their honey bees, brought in to pollinate the plants. The Africanized bees wreck this sweet arrangement. They get into hives of the honey bees to mate with them but don't let the honey bees into their hives; this aggressive mingling, which was once predicted to mute the killer bees' fierceness, has not worked too well.
The Africanized bees do not like to find all their pollen in one area the way the honey bees do. In fact, in Africa they are considered a nomadic species, so crops do not get pollinated. The Africanized bees also produce less honey.
Killer bees are hard to distinguish from honey bees at first sight. They are just 10 percent smaller and a tiny bit darker. Each one actually has less venom. They have shorter life spans but swarm more frequently to find a new hive. The only way you can tell if that bee coming at you is a killer bee or a honey bee is to see how much quicker they are to anger (30 times faster), or longer to forget that anger (30 minutes vs. 4 minutes). It is not clear how far north they can survive the winters - they have been adapting to cooler climates as they move north.
How to avoid stings
1. Stay away from honey bee colonies. Africanized bees sting to defend themselves or their nest. If you can avoid disturbing them in any way, they will not sting. Listen for the steady buzz produced by a colony and look for flying insects.
2. Wear appropriate clothing. When hiking in the wilderness, wear light-colored clothing. Killer bees respond most violently to anything that is dark-colored or fuzzy since their natural enemies are skunks and bears. Wear white socks, pants and a long-sleeved shirt if possible.
3. Avoid wearing perfumes or scents. Bees are sensitive to odors and perfumes. Soaps and after-shave lotions may either attract or provoke bees.
The best strategy is to run away as fast as you can. Get to the shelter of a house or car as quickly as possible. Because the bees target your head and eyes, try to cover your head as much as you can, without slowing your progress. Do not flail or attempt to swat the bees, just get away fast. If you are far from shelter, try to run through tall brush. This will confuse and slow them while you make your way out of the area. If you see someone being attacked by bees, encourage them to run away or seek shelter. Do not try to rescue them yourself; seek emergency help.
Once you are away from the bees, remove all stingers from your body. Do not pull them out with tweezers or your fingers, as this will only squeeze more venom into the wound. Scrape them out using your fingernails, the edge of a credit card or with a dull knife. If you are feeling ill, or if you have any reason to believe you may be allergic to bee stings, seek medical attention immediately.