Most animals have very short lives. But some live longer that people usually live. A tortoise has been known to reach the age of one hundred and fifty. Elephants grow old at just about the same rate as people. Many of them live to be sixty-five or seventy. Dogs and cats are old when they reach the age of ten, but some live longer. And one kind of insect — the seventeen-year locust — usually spends seventeen years in the earth before it comes out. Then it lives for only a few weeks.