The sheer number of plant and animal species on the planet can seem daunting but, says SIMON BARNES, we should take delight in this unknowable diversity. It means that we can be surprised - and make new discoveries - at every turn. I LOVE A GOOD BUTTERFLY DAY. i recall such a day last spring when I watched two orange tips, locked together in a crazy sort of flutter-fight, defy gravity between the high, sun-warmed hedges. I knew they were both males because only males have orange tips to their wings.I felt pretty smart knowing that. Mind you, I had to look up the females, who have small black tips to their wings, something I had never noticed for myself. When butterflies are emerging, I am truly able to relish my own ignorance. There are about 40 butterflies seen easily in this country, and I doubt if I could reliably recognise half of them. While this is admittedly poor, I enjoy butterfly days very deeply. And here's the point - my ignorance is an important aspect of my enjoyment.