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　　Sailors don't need to read the stars anymore—they've got GPS. But dung beetles¹ do not have GPS. And it now appears that they use the

　　Milky² Way

　　as a compass.

　　Dung beetles need a keen sense of direction so they can roll their dung patties away from the communal³ dung pile, and feast in peace. Ten years ago, Marie Dacke at Lund University in Sweden and her colleagues discovered that some dung beetles use polarized moonlight to keep a straight course. But what’s their plan on moonless nights?

　　Dacke tracked the beetles as they successfully rolled dung away from the center of a circular sandbox. Then she blocked the beetles' starry⁴ view with tiny cardboard hats, and set 'em loose again. Without stars to guide them, the beetles traveling twisted, circular paths. Those findings appear in the journal

　　Current Biology.

　　The beetles' tiny compound eyes probably aren't sharp enough to make out individual stars. In a planetarium⁵, for example, when only 18 bright stars were illuminated⁶, the beetles got lost. But the faint streak⁷ of the Milky Way seems to be just enough light to point them to a dung dining hole—no reservations required.

　　Thanks for the minute for Scientific Americans 60 second science, I am Christopher Intagliata

　　Patty: 小馅饼；肉饼

　　starry: 满天繁星的

　　planetarium: 天文馆；行星仪

　　streak: 一条

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