I will discuss the fable by picking out what I feel are relevant sections of the poem and then attempting to interpret them for the reader:
This section appears near the beginning of the poem, and describes the initial state of the thriving hive. It is thriving, according to Mandeville, because the bees have an insatiable appetite for consumption that is coupled with the freedom and ability of other bees to supply the things all desire to consume.
This is an early reference to the general moral of the poem. It was the insatiable need to consume (a vice), that was the source of the colony's power. In fact, this vice made the colony an object of envy by outsiders, leading to the outcome envisioned by those who proselytize virtue.
The seeds of the downfall of the hive are revealed here. The bees want to "have their cake, and eat it too." Since the vice of insatiable consumption is frowned upon by moralists, though it is the basis of the society's power, there is a kind of cognitive dissonance. According to Mandeville, those who fall behind in this competitive and fast moving society are likely to condemn the vices practiced better by others. This may or may not undermine consumption in good times, but it seems much more likely to prevail when the chips are down.