Which one is correct: an excellent article on ant behaviour or an excellent article about ant behaviour?
If both are correct, is there a difference in their meaning and usage?
Difference in usage is very subtle.
On would be a preference in many contexts. On is probably more common in spoken and written language, but I believe about might be a little more common in spoken language than it might be in written language.
I saw an ad banner that said: "Learn more on swimming with manatees." Say all you like that it doesn't matter which you use, but I feel strongly that "more about" would be preferable. As written, that ad makes the writer of it sound like, well, a "more-on."