New Delhi, Aug. 11 -- A single photo of a grassy patch is driving Reddit users up the wall this week. On first glance, it is just a close-up of green blades swaying in natural light. But somewhere in that tangle, a grasshopper has perfectly blended in, and spotting it is proving tougher than most expected.

The optical illusion image was posted in the r/FindTheSniper community, where these "find the hidden object" challenges usually get solved within seconds. Not this time. The insect's coloring matches the grass so closely that even people staring at the picture for minutes came up empty.

Camouflage is nature's own trickery, and grasshoppers are masters at it. Their mottled green-and-brown bodies mimic the texture of the vegetation they...