Kate Umbers was hiking through Australia’s Snowy Mountains in the autumn of 2008, when she saw her first mountain katydid—a thumb-sized insect with the colour and texture of a dead leaf.
“I recognised it from the guide books and picked it up excitedly,” she says. “It immediately vomited and flashed its bright colours.”
Emphasis on bright. The insect’s dull brown wing casings flew apart to reveal vivid bands of red, black, and electric blue.
The inconspicuous leaf suddenly transformed into a garish Christmas bauble.
Many animals do something similar. When a threat gets close, they flash bright colours, show off distracting eyespots, strike aggressive poses, and spray off-putting chemicals.
They hiss, rattle, puff, and arch. These spectacles are called deimatic displays and they are supposedly meant to distract or intimate predators. Bright colours, in particular, are often messages that scream:
“I AM TOXIC; DO NOT EAT ME.” For some animals, these claims are bluffs. For the mountain katydid, they are genuine warnings—this insect is full of foul-tasting chemicals.
But Umbers noticed something unusual about its displays: the katydid only flashed its colours after an attack.
“I was struck by how easy it was to catch them and how little resistance they put up,” she says.
“They waited until they had been grabbed before revealing any defences.”