Killer bees started in Brazil in 1957. A scientist in Sao Paulo wanted bees to make more honey. So he put forty-six African bees with some Brazilian bees. _ . But the new bees were a mistake. They did not want to make more honey. They wanted to attack. Then, by accident, twenty-six African bees escaped and bred with the Brazilian bees outside. Scientists could not control the problem. The bees spread. They went from Brazil to Venezuela. Then they went to Central America. Now they are in North America. They travel about 390 miles a year. Each group of bees, or colony  , grows four times a year. This means one million new colonies every five years. Why are people afraid of killer bees? People are afraid for two reasons. First, the bees sting (, ) many more times than a normal bee. Killer bees can sting sixty times a minute non-stop for two hours. Second, killer bees attack in groups. Four hundred bee stings can kill a person. Already several hundred people are dead. Now killer bees are in Texas. In a few years they will spread all over the United States. People can do nothing but wait. The bees bred and made a new kind of bee. Here "bred" means   _  .
attack run away died produce young