The “Let’s Talk About Parks” series is designed to encourage exploration and discovery of Pittsburgh’s urban parks.

The early fall in our city parks — especially warmer days — is full of interesting sounds such as birds chirping as they prepare for the coming cooler weather, squirrels and chipmunks gathering nuts to store for the winter, and noisy insects. The sound of katydids calling on a warm fall evening is a common sign that summer has come to a close and fall has arrived.

Katydids get their name from their scratchy call that many say sounds like “katy-did … katy-did-it.” Katydids — both male and female — make this sound by rubbing their wings together. Their lower wings have a sharp edge (the scraper) that they rub along a row of bumps (the file) on their upper wings to create the sound. It is easy to hear katydids but sometimes difficult to see them. This is because they often call from the high branches of trees and shrubs, and because they are nocturnal, which means they are most active under cover of night.

While most katydids are about two inches long when fully grown and bright green with brown or red accents, some have a different genetic makeup that turns them pink. If you spot a katydid, you can tell it apart from its similar-looking insect relative the grasshopper by its long antennae, which can be up to double its body length. Other ways to identify a katydid is by its long black legs and thickly veined wings that fold over its back. The size and shape — not to mention their green color — allows the katydid to blend in perfectly with grass and leaves. Even though they have beautiful wings, the katydid prefers to walk and climb instead of fly.

Leaves not only help hide them from predators, but they also provide food. Katydids have chewing mouthparts that allow them to eat foliage, including their favorite — oak leaves. A katydid’s legs are especially important because their ears — called tympana — are located on their front legs. These super-sensitive ears allow them to pinpoint the location of potential mates, as well as potential competitors for mates.

And even if you are far from a Pittsburgh Park, or your own backyard, you will likely still find katydids. They have been spotted on every continent around the world except Antarctica.

First Published: October 6, 2015, 4:00 a.m.