Insect is signed exactly like bug: place your thumb on your nose with your index finger and middle finger extended. Bend and extend your index and middle fingers, wiggling them as a bug would move its antennae. It looks a little like an insect has landed on your nose.
We often introduce insects by using the generic sign for insect. As your baby gets more advanced with his signing, we start using more specific signs like spider and ant.
We use the sign for insect when trying to give our babies a general word to describe bugs. Once our babies are able to differentiate between different insects, we introduce signs for different bugs commonly found in our garden or around our house.