In the short story "Expendable" by Philip K. Dick, the protagonist is a man who can communicate with spiders. At one point, after fighting off a home invasion by an army of ants, the protagonist is seated at his desk, armed and despairing, when a spider drops by to talk to him.
The spider slid down beside him onto the desk top. "Sorry. Hope you aren't frightened, as in the poem."
What does this line mean? Is there some famous poem about a man being frightened by a spider landing beside him, or by facing an invasion of ants? If so, is the spider actually supposed to be familiar with literature?