As busy as a bee
From Chaucer's Canterbury Tales, (the Squire's Tale), 1386-1400:
Ey! Goddes mercy! sayd our Hoste tho,
Now such a wyf I pray God keep me fro.
Lo, suche sleightes and subtilitees
In wommen be; for ay as busy as bees
Be thay us seely men for to desceyve,
And from a soth ever a lie thay weyve.
And by this Marchaundes tale it proveth wel.
"See other 'as x as y similes'.