Katydids Have Ears on Their Legs

Forget everything you know about ears. While humans keep their hearing apparatus sensibly located on their heads, katydids decided to take a radically different approach. These green, leaf-shaped insects hear the world through a pair of small oval slits on their front legs—specifically on the tibia, just below the knee joint.

It sounds like a biological joke, but it's devastatingly effective.

How Leg-Ears Actually Work

The openings on a katydid's legs are called tympanal organs. Each one contains a thin membrane (like an eardrum) stretched over an air-filled chamber. When sound waves hit these membranes, they vibrate, sending signals to the katydid's nervous system.

What makes this truly remarkable is the precision. Katydids can detect:

• The ultrasonic calls of potential mates
• The echolocation clicks of hunting bats
• Frequencies ranging from 5 kHz to over 100 kHz

Some species can hear sounds five times higher than the upper limit of human hearing.

Why Legs Make Sense

Having ears on your legs isn't as absurd as it sounds. For an insect that spends its life clinging to leaves and branches, leg-mounted ears provide a crucial advantage: directional hearing. By comparing the sound arriving at each front leg, a katydid can triangulate exactly where a call is coming from.

This is especially important during mating season. Male katydids produce their distinctive calls by rubbing their wings together, and females need to locate them quickly—before a predator does.

The Bat Problem

There's a dark side to having such sensitive hearing. Bats love eating katydids, and they hunt using echolocation. So katydids evolved to hear bat frequencies too.

When a katydid detects incoming bat sonar, it can take evasive action—folding its wings and dropping from its perch. Some species have even evolved to produce calls that are outside the frequency range most bats can detect, essentially whispering their love songs.

It's an acoustic arms race that's been playing out for millions of years.

Not Just Katydids

Leg-based hearing isn't unique to katydids. Their relatives, crickets, also have tympanal organs on their front legs. But katydids have taken the system further, developing some of the most sophisticated insect ears known to science.

One species, Copiphora gorgonensis, was discovered to have ears that work almost exactly like mammalian ears—complete with a lever system that amplifies sound. Scientists didn't believe insects were capable of such complexity until they examined these katydid ears under high-powered microscopes.

So next time you hear the rhythmic chirping of katydids on a summer night, remember: they're not just making noise. They're engaged in an intricate acoustic conversation, heard through ears that evolution decided to put in the last place you'd expect.