MEMETERIA by Thomas May

I’ve been working on a note for Howard Hanson’s most-popular composition — the Symphony No. 2 (“Romantic”) from 1930, a Boston Symphony commission (same vintage as Stravinsky’s Symphony of Psalms).
And this is an earworm I cannot dispel (the second theme from the first movement, which cycles back several times later on):

So what is it that makes for an earworm?