The bee is a symbol of diligence.
Did I use the articles correctly? Is it possible to use 'A bee' and 'the symbol' in this sentence?
'the' is correct since the sentence is not referring to a single bee, or a particular bee (which would then also take 'the'), but to 'bees' as a species.
Probably 'a symbol' is better here, since the bee is not the sole symbol of diligence - ants and beavers are up there too. - though admittedly, the saying is, 'busy as a bee'.