Glowing in the dark

For the past couple of years I've watched the tree at the end of my garden light up at night with a soft fluorescent glow.
For ages I presumed it to be fairy lights in the neighbours tree shining through; they have young children and presumed why not.
At least I presumed.
Last night I remembered I had left the greenhouse door wide open and with the number of cats out on the prowl, decided it would be best if I got out of bed and close it.
Little did I know the past midnight foray would answer a question I hadn't realised I asked.
Fireflies sat in the tree emitting their bio-luminescence in the hope of a quick, hot, date with the opposite sex.
It was truly magical and I stood in complete wonder at the sight.
Yawning, and hopefully thinking of my bed, I closed the greenhouse door and went back to bed.