Katydids are medium-sized to large insects. They are usually green, sometimes with brown markings. They have a thick body, usually taller than it is wide, and long thing legs. The hind legs are longer than the front or middle legs, and are often used for jumping. On the head they have chewing mouthparts and long thin antennae that reach back at least to the abdomen of the insect. The adults of some katydid species can fly, and all katydids are camouflaged to blend with the leaves they feed on.
In all species the front wings have special structures that can be rubbed together to make sounds. They hear these sounds with flat patches on their legs that act as ears.
Females are usually larger than males, and have a long sharp structure at the end of the abdomen. This looks like a stinger, but it is actually an "ovipositor." They use if for sticking their eggs into the ground or into plant stems.
There are hundreds of katydids species, and they are found all over the world. As with most insect groups, the greatest richness of katydid species is in tropical areas. In Michigan we have about 20 species.
Katydids spend most of their lives on the plants that they eat, so they need habitats with lots of plants. They can live in lots of different climates, so any habitat with plants usually has at least a few katydid species.
Katydids have incomplete metamorphosis. The nymph that hatches from an egg looks a lot like an adult, except that it doesn't have wings. As they grow, katydids shed their exoskeletons (this is called molting). In their last molt, they get wings and they become adults. After that they stop growing and don't molt any more.
Most katydid species live for a year or less. Only one stage in the life-cycle (usually the eggs) can survive the winter. In the tropics some species can live for several years.
Some katydid species are active during the day, but most are nocturnal. They can move around more then without being spotted by predators. Katydids are not social, they don't live in groups.
Katydids use sound to communicate across distances. Sometimes nearby males will all call together, trying to attract females. They also use their antennae to touch and smell each other. They can see too.
Katydids are primarily leaf-eaters. They sometimes eat other plant parts (especially flowers). They also sometimes eat dead insects, insect eggs or slow-moving insects like aphids. In the tropics some species are quite carnivorous.
Katyids rely on their excellent camouflage for protection. They can also jump very quickly, and spend most of their time in trees and bushes. The adults of some species can fly.
Katydids don't have much to do with humans. They are interesting to watch and listen to, but they don't have many direct effects on humans. Sometimes they damage crop plants, but this is rare.
No katydids are considered endangered. Some have become more rare because they need particular kinds of habitats or food plants.
Some people think that the call of some katydids sounds like someone calling out the words "Katy Did! Katy Didn't! Katy Did! Katy Didn't!" That's where the family gets its common name.