Killer bees

The Africanized Honey Bee is a hybrid of one of the several European Honey Bee subspecies (Apis mellifera mellifera, A.m.carnica, A.m.caucasia, or A.m.linguica) and the African Honey Bee (Apis mellifera scutellata).

The Africanized Honey Bee, more popularly known as the "killer" bee, has the general appearance of the more temperamental European Honey Bee (Apis mellifera). However, they are slightly smaller, but only microscopic measurements in a laboratory would be able to distinguish between the two. They are robust, 3/4 of an inch in length, and are covered in fuzz. They are brownish in color with black stripes that aren't as distinct as those on wasps or hornets. They have four clear wings that are attached to the thorax, which is the middle section of the body. The six legs are also attached to the bottom of the thorax. The abdomen is larger than the thorax and ends in the stinger, and the head is smaller than both of the sections. The two compound eyes are large and bulbous and allow the Africanized Honey Bee to see ultraviolet rays, enabling them to fly at night. The queens are the largest bees in the social structure, followed by the drones and then the workers.

History of it
In 1956 African bees were brought to Brazil so that scientists there could try to develop a honey bee better adapted to tropical areas. Unfortunately, some of the bees escaped and began breeding with local Brazilian honey bees. Since 1957, these bees and their hybrid offspring, Africanized Honey Bees, have been multiplying and migrating to other regions.
The first swarm of Africanized bees in the United States was documented in 1990 at Hidalgo, Texas. They were found in Arizona and New Mexico in 1993, California in 1994 and in Nevada in 1998. As of this writing, Africanized Honey Bees can be found in most of mid and southern Texas, about one-third of New Mexico, all over Arizona, the southern half of New Mexico and the southern third of California. They continue their northward migration.
About the Bees
The sting of the Africanized Honey Bee is no more potent than your garden variety honey bee and they look pretty much the same. What makes AHBs more dangerous is that they are more easily provoked, quick to swarm, attack in greater numbers, and pursue their victims for greater distances. The AHB colony can remain agitated longer and may attack up to a quarter of a mile away from the hive. AHB colonies can be very large, and they are not particularly selective about the location of their hives. The Queen Africanized bee can lay up to 1,500 eggs a day.
AHBs are likely to develop near canals, drainage ditches and retention basins because they like to be near water. When they sense rain, they swarm.
In Arizona, the AHB colonies have grown and the more aggressive colonies are the ones that have survived the droughts of the past few years. The summer is the peak period for bee attacks because there is less honey, and the bees become more protective of their hives.