I got this wrong and when the correct version came up at the bottom it said Există, not sunt. I think that is a new word and it is rather confusing to have two versions of the same sentence given as the correct one.
Several problems. "Insecte" is plural, therefore it cannot be either "el" or "este". Also, this sentence is about sole existence ("there are"), not about what something is (e.g. "it is") - so you shouldn't present an extra pronoun at all.