Meet the Beetle That Shines Like Gold and Changes Colour to Outsmart Predators

22 November 2025

Tortoise beetles, found in shades of metallic gold and green to matte red and brown, are named for their dome-shaped shells resembling those of tortoises.

This hard shell is called a carapace.

Priyanka Ghosh, senior research fellow at the Zoological Survey of India, Kolkata, who has studied the creatures, points out, “These beetles have the most interesting ability to change the colour and reflectivity of the carapace.”

The phenomenon is called ‘optical defence’.

During field collections, Priyanka observed that the green, patterned Cassida circumdata, green, spotted Chridopsis bipunctata, and Cassida viridis change colours from green to brown as a defence mechanism against predators.

The mechanism of colour change is complex and different from that of chameleons or marine animals.

Meanwhile, the golden tortoise beetle (Charidotella egregia), native to America, changes from a metallic golden to a matte red in 90 seconds when disturbed.

The beetles actively move fluid or water out of their forewings’ outer layers for this transformation.

These small beetles showcase how evolution combines form, colour, and behaviour into a remarkable survival strategy.

Maybe the next time you’re in a garden, turn over a leaf and look underneath at a wonderful tortoise beetle you share the world with.

This story is part of a content series by The Better India and Roundglass Sustain.