They certainly are! I have a selection of books, websites and facebook groups to help with identifying them.
Some are really distinctive and easy to ID, some others look quite similar and can be difficult, and some others are impossible to ID from a photo, so an expert needs to kill and dissect them. Its an important part of studying insects, but its not something I do.
Those Cinnabar caterpillars are an example of a distinctive species... literally nothing else in the UK looks like those