In the cool hour after sunrise on 5 August, a scorching day during the heatwave, I watched shafts of sunlight piercing the hedge, sweeping across the garden. For a moment, a spotlight fell on a garden spider’s half-finished orb web, its owner threading the final silken spiral on to radiating spokes. As the sun rose, the sunbeam shifted and the snare became almost invisible, a deathtrap for any passing insect. A small, vulnerable butterfly, jinking between the shrubs, settled on a conifer branch nearby: a newly hatched holly blue, with immaculate wings like pale azure silk. Holly blues reach their northern limit near this latitude. They are typically wanderers, commonest in southern, sheltered suburbs. From the middle of the 19th century until the late 1940s there were only three sightings in north-east England. Then they disappeared again for the rest of the century. I saw one in Newcastle in 2014, another in Sunderland in 2018. Since 2019, they have turned up annually in our garden in south-west Durham. The warming climate seems a likely reason for their return, but they may need more than milder winters to save them from local extinction. Holly blues have two generations each year. Caterpillars hatching from eggs laid by adults emerging in spring feed on holly; those of second-generation adults in autumn feed on ivy flower buds. When this year’s August hatching occurred, there was no sign of flower buds on our ivy. Completing the annual cycle depends on developmental synchrony between butterfly hatching and availability of its larval food plant for egg laying – would our holly blue survive until ivy buds formed? Twenty-four days after hatching, our tenacious holly blue is still feeding on marjoram flowers, dodging spiders’ snares, avoiding birds’ beaks and sheltering under leaves during torrential downpours. In the 1950s, L Hugh Newman, a lepidopterist who bred butterflies for Winston Churchill’s garden at Chartwell, compiled records of butterfly life expectations. He found that holly blues typically survived 14 to 16 days, so ours is in its dotage. Those lustrous wings, now a little threadbare, still flash with azure iridescence in sunlight. Then, today, I watched it laying eggs among ivy inflorescences in the hedge.