Mary Howitt’s poem “The Spider and the Fly” is a fable in verse that delivers a lesson — never pay heed to flattery of an evil counsellor. The poetess herself conveys this message rather directly in the very last stanza of the poem.

The poem basically tells us a tale of a spider and a fly where the spider successfully seduced the fly by flattering words and trapped it as a prey. So the theme here is the power of flattery — the destructive effect of vanity. It has been a cautionary tale against those who use flattery and charm to disguise their evil intentions.

(Follow the above link for a detailed write-up on this.)