I did not expect to see her. There was barely any sunlight and a loose wind-beckoning rain. It had been grey for days. She seemed lost and so alone - the only one of her kind to have been born now, the others still in their chrysalis, gambling on certainty waiting inside for warmth. Yet there she was, unsteady in the air above the mud.

I watched her. I wanted to be sure that she was real. When she landed, I put my hand around her. As a boy I learned to be gentle with butterflies; they are teachers of gentleness. Then I could see the shape of her wings, like a harlequin, or a seashell, the outline mimicking the outer edges of a leaf, and the one orange spot on her lower wings. She was barely yellow, one drop of lemon that is all, completely demure. Not like the males, who are visible from hundreds of yards, brilliant, the colour of sunshine, flying buttercups. I thought maybe that is why they were named ‘brimstones’ but it is the old name for sulphur, the exact colour of the male’s wings. And in March, on a grey day, yes, she was alone.

Brimstones are the first butterflies to fledge - earlier than blossom, and even birdsong they announce that spring is here. As our climate warms these beautiful butterflies are making their way slowly northwards a mile or two a year. But it is not in any way a safe journey into the air.

Butterflies are food for birds, lizards, spiders, snakes and mice. I have seen domestic cats catching and eating butterflies. Probably the most gruesome predators are small wasps. One species lays its eggs within the cabbage white butterfly which is then literally consumed from the inside. Out of around 400 eggs laid by a female butterfly only eight will make it onto the wing. Brimstones have an exceptionally long life span from egg to butterfly; some live for well over a year.

But this female brimstone on this day felt so vulnerable. When I opened my hand, she didn’t fly for long. Maybe she had just emerged and was finding her balance, her bearings. She almost limped into the air and then headed into the undergrowth and crawled onto the underside of a leaf where she hung upside down. This was a sure sign that rain was on the way.

But it was her life force that was exquisite, this fragile being wrapped in nothing, her wings as thin as petals. Recently, I finished reading The Observer’s Book of Common Insects and Spiders. It’s more of a reference book really but as I read it from cover to cover, I became aware of the existence of another realm of beings and the borders of their worlds. Pondscaters, Robber flies, Rose chafers, Midges, Musk beetles. Here is a symphony of life, each one laced with jeopardy and risk. I walked on, encased in waterproof, gloves, a phone in my pack, and sturdy boots on my feet. And compared to this female brimstone, no, I cannot match her strength or, indeed, her dignity.