A Rainbow Foundation

Once a spider built a cobweb on a rainbow bright and gay,
For she thought its brilliant colors would entice her lawful prey.
But, alas! the sun descended, and the bright bow was no more.
And the weeping, webless spider was left homeless as before.
“After this,” I heard her mutter to herself, “I’ll be content
With foundations not so showy, but more firm and permanent!”