Locus are a larger version of a grasshopper. When they breed they do it abundantly and they can cause serious crop damage when they fly in swarms. By the way this would be more of a science question. ;)
Your second question is a history one: I believe the answer is Nelson Mandela. He was the first democratic president of the Republic of South Africa. He was "sworn in" in 1994 at the age of 74 or 75 I believe.
