The butterflies in the control group were painted and cut in a way to leave their eyespots and sound-producing structures intact.
During the 30 minute trials, all butterflies were found and attacked by the birds.
"Eyespots alone, or in combination with sound, constituted an effective defense. Only one out of 34 butterflies with intact eyespots was killed, whereas 13 out of 20 butterflies without eyespots were killed," wrote the researchers.
There was no difference in survival between butterflies with or without sound.
"Our experiments do suggest that the hissing sound is not of crucial importance to the peacock butterfly when defending itself against the blue tits," concluded the researchers.
According to entomologist Enzo Moretto, director of the Butterfly Arc, which houses more than 400 butterflies near Padua, Italy, further studies are necessary to fully establish the eyespots' defensive function.
"It has long been assumed that butterfly eyespots have an intimidating role, but we still lack of a wide experimental evidence on how effective this bold displaying of eyespots is. And we do not know if all predators startle," Moretto told Animal Planet News.
Name: Peacock Butterfly (
Inachis io)
Primary Classification: Lepidoptera (Butterflies and Moths)
Location: Temperate Europe and Asia, and occasionally North America
Habitat: Woodlands and gardens
Diet: Sap flows, rotting fruit, dung and nectar.
Size: Around 2-2.5 inches from wingtip to wingtip.
Description: Chocolate brown body; orange-red wings with blue, peacock-like spots.
Cool Facts: It is highly adapted to human civilization, feasting on nitrogen-rich waste and nectar from garden beds.
Conservation Status: Common
