A finch in Ecuador’s Galapagos Islands pulls a cotton ball from a dispenser set out by scientists. A University of Utah study showed that when the cotton is treated with permethrin – a mild pesticide used in human head-louse shampoo – and the birds use the cotton in their nests, blood-sucking fly maggots are killed, thereby protecting the finches and their offspring that often fall prey to the maggots. A finch in Ecuador’s Galapagos Islands pulls a cotton ball from a dispenser set out by scientists. A University of Utah study showed that when the cotton is treated with permethrin – a mild pesticide used in human head-louse shampoo – and the birds use the cotton in their nests, blood-sucking fly maggots are killed, thereby protecting the finches and their offspring that often fall prey to the maggots. Photo Credit: Sarah Knutie, University of Utah