Deterring Ticks with Citrus and Millipedes

Why do birds, monkeys and other animals rub themselves with citrus and creatures like millipedes? One likely reason is because certain plants and arthropods contain natural repellents.

Scientists with the U.S. Department of Agriculture (USDA) and the Smithsonian Conservation Biology Institute (SCBI) at theNational Zoological Park in Front Royal, Va., examined citrus compounds and millipedes