There is a species of beetle that has two different color phases. Some have dark, purplish shells with green spots on them; others (same species) have greenish shells with purple spots on them, and there are other varieties that are somewhere in between. The beetles feed on the garden plants and the birds in the area feed on the beetles. When Mr. Jones bought his 200 acre farm, most of his farm was overgrown with an invasive vine that had purple stems and leaves. As he set to work removing these vines so he could farm the land he found many of these beetles on his land. Most of them were the purple color phase, with the occasional green beetle here and there. After several years and lots of hard work he had removed all of the purple vines and replaced them with green soybeans and corn plants. By this time, when he was working in his fields, he noticed that he still saw lots of the beetles, but very few of them were purple. Instead, most of them were the green color phase.