BRING IT In females of the beetle Onthophagus sagittarius, competition for dung to wrap eggs and feed young favors the evolution of exaggerated horns.
Sean Stankowski
VENUS AND MARS Both of these dung beetles belong to the same species, but the horns of the female (right) lie centrally positioned like a rhino’s and probably evolved independently from the side-by-side horns of the male (left).
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