Katydids (Family: Tettigoniidae). These cryptic insects are closely related to crickets and grasshoppers. Just like their cousins, they can jump, sometimes fly, and produce noise. Katydids, also known as bush crickets, are generally green and leafy shaped with long antennae.
These nibble on plants and cause similar damage to other insects with chewing mouthparts such as caterpillars.
Katydids are most active during the spring through to fall. You can hear their songs on warm evenings.
Katydids are distributed worldwide but are most abundant in tropical locations.
While some katydids are predaceous most are herbivorous, meaning they feed on plants. That said, tomato plants are not usually on the top of their list. However, if it is the only plant around they will feed on them.
If you see a couple of katydids around your plants, I would not worry too much. They are not known to be devastating pests of tomatoes. Some even eat other insects so their presence may even be welcomed! If you are worried, you can always move them to another plant or relocated them.
Katydids can have amazing camouflage. While most look like leaves, several also mimic moss, lichen, and bark! They are harmless insects that use their cryptic coloration to hide from predators. They are mostly nocturnal, feeding and roaming around mostly at night.