As I sat by my father’s bed in the hospice, holding his hand in the final hour of his life, I found myself talking about butterflies. But who really knows what to say at the end? He was seemingly insensate, his vacant face unfamiliar and chilling. For the first time in my life he didn’t quicken to my attention, didn’t rise to the occasion of being Dad. I told him that I loved him and that I wouldn’t leave him. I kissed him. I wept. And then I told him about a small tortoiseshell I had seen in his garage just two hours earlier.

I didn’t tell him it was the separated wing of a dead butterfly, a memento mori buried behind a pile of logs I was shifting for my mum. The significant thing was that I had named a butterfly. Just a few weeks earlier, Dad would have considered this a small miracle. He was probably hoping for a more useful miracle in that particular moment, but I am sure I felt his hand flex in mine. For once he wasn’t in a position to doubt my identification (to be fair to him, until that summer, I would have said it was the wing of a red admiral). But he didn’t need to question me any more. A transformation had taken place.

Ever since I was a small boy my dad had tried to share his love of the natural world with me, and until the spring of 2020, when he was given a terminal cancer diagnosis, he had failed. But in the last six months of his life, I became obsessed with one of his chief passions: butterflies. What had changed?

I had always found his interests in natural history a bit boring, sometimes embarrassing. I look back now and bitterly regret my adolescent dismissiveness and all the opportunities it squandered. But surely no one could withstand their dad talking about things like a butterfly’s jizz – a term transferred from birding to describe a species’ distinctive appearance and style of flight. Maybe I had matured. Maybe, as a new father myself, I wanted to be able to share the kind of knowledge I had taken for granted in him with my son. Maybe butterflying was simply my escape from the restrictions of the pandemic. Maybe it was all these things.

It was also an attempt to be his connection to the outside world, now that he was housebound. All through that burning, terminal summer, I walked the woods and fields of Northamptonshire, out of my element while self-consciously in his, following his tips. I’d return to his bedside in my role as a carer and now as proxy in the field, with stories and reports of what I had seen.

This involved entering unfamiliar territories, trying not to submit to a creeping sense of impostor syndrome. I tiptoed around Fermyn Woods in northeast Northamptonshire, hoping to see the celebrity of the British butterfly kingdom, the purple emperor. I was desperate to avoid the attention of the cognoscenti with their long-lens cameras, talking about jizz. Some characters were unavoidable, like the man scanning the bushes in a trance-like state, followed by the man who had poured a bottle of urine around the base of an oak tree and avoided deodorant for two days, all in the hope of attracting emperors.

Purple emperors have notoriously foul tastes, and devotees will go to great lengths for a meet-and-greet with one. Later that day I was crouched around a dog turd with several strangers, all eyeballing a famous butterfly as if we might be able to give it (and by collateral the turd) a kiss. All I wanted was a photo. I managed to send one to Dad as soon as I got back to my car. As always, his response was rapid: Well done. Keep it up. I’m living through you now xx.

I spent as much time as I could that summer searching for hairstreaks, skippers, fritillaries and admirals, eager for things to impress Dad with. He had bigger things on his mind, but he was pleased to see my eyes opening at last. I hesitate to say that nature had become a solace. I’m sure it had, in some sense, but it feels a little clichéd, too, like a Disneyfication of what was in fact a terribly difficult time. I don’t deny that nature can serve as cure or restorative, but it can also trouble and mystify and disconcert and shock and disrupt. My experiences in nature while Dad was dying were often ecstatic, but they were also tinged with melancholy, frustration, boredom and other less idealised feelings that I now realise were crucial elements in the whole transformation.

I found myself photographing tatty butterflies with bits of their wings missing, time-worn and vulnerable, as if deteriorating under the weight of their own symbolism. The butterfly is one of our most resonant metaphors for transformation, the distinct stages of its lifecycle taught in songs and stories from childhood. But the metaphor was no longer straightforward to me. While I was out chasing butterflies, as if they might transform Dad’s condition or defer the inevitable, he was at home, in bed, shedding his recognisable forms. I bathed him in his final weeks, emptied his urostomy bag down the toilet, cut his nails, wiped his nose bleeds; and when I helped him down the stairs to the ambulance waiting outside, leaving the home he had built for the last time, I was repaying him for a life of being carried myself.

I couldn’t help thinking about time and the generations. I imagined my son, myself and Dad in the sequence of metamorphosis – my son as caterpillar, Dad as butterfly, and me as the in-between chrysalis, in some ways the younger form of the butterfly, but also somehow the parent of it, as if more aged than what comes next, complicating the natural order. Who is the parent and who is the child? That old cliché.

I began to question the butterfly’s pertinence as a symbol of possibility, of better times, of the triumph of beauty. Isn’t the butterfly’s cycle also emblematic of fixed outcomes, trapped in its own blueprint, each specimen identical with its species, as if they’re all turned out by the same big printer? Maybe it was the inescapability of Dad’s terminal condition that had me thinking that way, overwhelmed by anticipatory grief, mourning the loved one before they are even gone.

But Dad was still on hand to restore me to more magical thinking. I received a text message one day saying he thought he could manage a very short walk, having been unable to get out all summer. He wanted to show me something special. We went to a treasured wood near my parents’ house, in disbelief that we were finally butterflying together, wishing we had done it sooner when all these gifts had been freely on offer, now coming at such a price.

At the start of a footpath that edged woodland he had stalked as a child with his father, Dad pointed out a tree (a bullace, apparently) – we won’t get far, I thought, if he’s going to name each individual tree. “You’ll find black hairstreaks in there in June,” he said. Next an oak where, he told me, I would find purple emperors in July. And finally, off the path into the heart of the wood, trees closing overhead, where we might find the scarce and endangered wood white. I now realise he was preparing me for a time when he would be gone, passing down, at the last possible moment, years of local knowledge acquired through patience, attentiveness and trial-and-error. “I’m going to have to turn around,” he said after too short a time, having seen no wood whites, fatigued and forlorn. We both tried to hide our disappointment – he didn’t like to let me down, and I just wanted the memory of a butterfly to cherish once he was gone.

The endangerment of the wood white spoke of Dad’s condition. But while nothing could be done to save him, there were things to be done to help the butterflies. Dad told me how he had recently sent an email to a local landowner who perhaps didn’t appreciate what he had in his woods, advising him on how to conserve the wood white. While it’s difficult to feel anything but depressed by the overwhelming decline in butterfly numbers, Dad’s attempt to protect these special creatures, as his own life dwindled, restored the metaphor of the butterfly cycle with hope.

Just as we approached the portal out of the woodland and back on to the footpath, Dad came to life. “There,” he said. “See it?” A delicate spectral butterfly, dancing languidly around the edge of the ride, and then a second, as if the wood whites had come to companion their old friend safely from the woods, bidding him a final farewell. I’ll come back for you, I thought. And I have done every summer since.

The Flitting by Ben Masters (Granta, £16.99) is available from guardianbookshop.com for £14.44