Insects navigate long distances with remarkably high precision despite their tiny brains and limited sensory capabilities. Many nocturnal insects rely on celestial cues—specifically, the direction of polarized light from the night sky—to maintain an accurate course for migration. Although scientists understand the insects' ability to extract a compass direction from polarized light in general, exactly how they determine that compass direction has remained a mystery.

Here, researchers report computer simulations indicating that the key lies in the tiny bumps known as corneal nipples that form in a hexagonal lattice across the surface of insect eyes. By analyzing how this geometry changes the patterns of the neural signals emitted by retinal neurons in response to incoming polarized light, they show that this structure acts as a high-sensitivity compass mechanism specifically suited to the insect visual system. They confirm this conclusion with neural recordings indicating that the neurons of the insects produce an output signal encoding celestial compass direction precisely as their computational model predicts.