Most bees are relatively harmless and beneficial, even vital for plant pollination, but the Africanized honey bees are dangerous and sometimes deadly. (See the story of the recent death of a Tucson man from massive bee stings here.)
Bees evolved from wasps. Bees are vegetarians that feed on nectar and pollen. Wasps are carnivores. In the Sonoran desert of Arizona, there are approximately 1,000 species of native bees. In the U.S. there are about 5,000 bee species.
According to the Arizona-Sonora Desert Museum:
Except for the parasitic cuckoo bees, all female bees make their living by foraging in search of protein-rich pollen and sugary nectar from flowering plants. By moving pollen around from flower to flower and plant to plant, bees perform vital and often unappreciated roles as the most important group of pollinating animals on earth. Yet bees are not out to “help” flowers; they collect pollen and nectar in order to feed themselves and their larvae.
Of the approximately 640 flowering plant taxa growing in the Tucson Mountains near the Desert Museum, approximately 80 percent of these species have flowers adapted for and pollinated by bees. Similarly, at least 30 percent of our agricultural crops require bees to move pollen between flowers. Not only are we dependent upon these “forgotten pollinators” for over a third of our food, but for other products as well. Cotton cloth is a product that eventually results from bee pollination, and so are many beverages and medicines made from other fruits and seeds.
Without the pollination services bees provide, many plants would not produce seed-laden fruits from which the next generation of plants would grow. Without bees, there would be few or no fleshy berries or fruits to sustain birds, mammals, and other wildlife. The tunneling activity of bees aerates the soil and allows water from infrequent rains to quickly penetrate and reach plant roots; and bees’ nitrogen-rich feces fertilize the soil. The bees themselves often provide food for lizards, mammals, birds, insects, spiders, and other arachnids.
In their daily quests bees harvest foodstuffs from flowers for themselves and their larvae. Pollen is a rich food source of amino acids, proteins, fatty acids, vitamins, minerals, and carbohydrates. Nectar provides the energy boost from sugars that bees need to fly. Some desert bees (Centris) have specialized scrapers on their legs for harvesting oils from glands on the undersides of specialized flowers in the ratany and malpighia families. These energy-rich oils are mixed with pollen as larval food and are also used to help construct brood cells. Other bees collect small pebbles, plant hairs, or floral resins that they use as building materials. Some bees, such as mason bees in the genus Osmia, also require water and mud with which to construct their adobe-like nests. Leafcutter bees (Megachile) remove circular pieces of leaves to fashion into cell walls. For more information, see the complete ASDM article here.
Most bees dig burrows in the ground, but some species use holes and tunnels made by other insects, especially beetles. The carpenter bees, those big black bees, may excavate there own holes in wood.
Most bees are solitary. Socialized bees in our region include the introduced honey bee, Africanized bees, and the native black and yellow bumblebees. For all bees, only the females sting. The stinger is an adaptation of the ovipositor, or egg laying structure. If the barbed stinger is left in the victim, the act usually rips the abdomen of the bee and causes it to die. There is some speculation that stingers evolved for inter-hive combat and in that case the bee did not lose the stinger.
A concise history of Africanized bees is available from DesertUSA:
Africanized Honey Bees (AHB) — also called Africanized bees or killer bees — are descendants of southern African bees imported in 1956 by Brazilian scientists attempting to breed a honey bee better adapted to the South American tropics.
When some of these bees escaped quarantine in 1957, they began breeding with local Brazilian honey bees, quickly multiplying and extended their range throughout South and Central America at a rate greater than 200 miles per year. In the past decade, AHB began invading North America.
Africanized bees acquired the name killer bees because they will viciously attack people and animals who unwittingly stray into their territory, often resulting in serious injury or death.
It is not necessary to disturb the hive itself to initiate an AHB attack. In fact, Africanized bees have been know to respond viciously to mundane occurrences, including noises or even vibrations from vehicles, equipment and pedestrians.
Though their venom is no more potent than native honey bees, Africanized bees attack in far greater numbers and pursue perceived enemies for greater distances. Once disturbed, colonies may remain agitated for 24 hours, attacking people and animals within a range of a quarter mile from the hive.
See the link above for the entire article.