Two evenings ago, a male purple emperor butterfly flew into my living room in south-west London. Although he was gone in less than a minute, it was still an absolutely magical encounter, and one I'll remember for many years. I didn't get time to take a picture, but imagine a large, strong, inky-dark butterfly, its wings shot through with deepest violet and laced with white.
Purple emperors are rare and elusive, spending much of their time in the tree canopy except for rare visits to the ground to feed on dung and dead animals. I saw one once, as a child, and have never forgotten the thrill of it. I didn't expect to see one in Streatham.
The timing couldn't have been better, though, as right now the Big Butterfly Count is on. You can download the free iPhone app and do your own 15-minute count any time between now and August 11.
I did my count on Tooting Common this morning. I expected to see maybe a couple of meadow browns, but in fact I spotted nine butterflies: large whites (or, as I've always known them, cabbage whites), gatekeepers, speckled woods and ringlets.
It's not only a nice example of citizen science (and one with genuine benefits for conservation) but a good way to engage with the natural world, particularly for children. Download the app here.