When you've learned all about invasive species, we challenge you to have a go at the Project UFO crossword! Just click on the crossword thumbnail and it will open in a new window.

Be warned though: it's pretty tough — in fact, Nine Down is a real stinker! But the correct answers can all be found on this site ... don't forget to visit the Glossary if all else fails. Good luck!

The answers — if you really, really need them — are here...

[See answers in new window]