Apple by John Baxter. I read it in the anthology New Writings in SF 10.
The story starts:
The apple was red, smooth, coldly perfect. One patch, almost obscured by the shadow it cast in the soft light, was green, a blemish that served only to show up the flawless purity of the remaining colour. It lay on its side, letting light spill into the recesses of its hollow, from which the stalk jutted inconclusively, terminating in a small leaf, greenly transparent.
Low down, near the ground, a crater had been gouged out, exposing the white flesh. The hollow was an irregular one and already the air had turned most of the higher points to a rusty brown. Much of the rest was creamy with incipient decay.
A town lay just under this crater, half its three hundred houses in morning sunlight, the others obscured by the dark terminator of the apple’s vast shadow.
To Billings,standing three miles away, it looked as if the apple itself were getting ready to snap up the rabble of houses over which it hovered, but when he looked up at the mass of the fruit looming solid and red in the strengthening light, its colour accentuated by the climbing sun, the sensation passed. It was as solid and immovable as the others.
Billings is a Moth Killer:
The men who hunted Moths were different. They had an understanding with the universe, a heightened sensitivity to the world off which other men merely scavenged. The thick white messy bulk of the apple was a place with its own rules in which Billings was comfortable, at home. He recognised the risks, but they were risks of the apple and of nature, not of men. He faced death, but it was nature's death, not man's.
However there is no young rival waiting. The story ends:
They never found his body as they had found that of his father but it was there for them to find if they had cared to look. Deep in the apple he lay cocooned in her web, his face looking out at her dried carapace. Long dead in the cold currents of autumn that, even deep in the core, she had felt and responded to, she left behind a final sign for him to ponder. Deep in his body the larvae lay that would one day rise to be another Moth, inhabit another apple, just as she had risen from a Moth Killer’s body herself, and others would rise after her. Though dead, Billings sensed the last great possession of his life and was content. Staring into the silent chambers of his tomb, he waited for resurrection.