What it meant to excommunicate a swarm
In the legend, Bernard does not swat the flies or explain their sudden disappearance: he pronounces an ecclesiastical penalty. Excommunication ordinarily meant exclusion from the Church’s community and its religious rites. Applying that word to insects gives the story its startling twist—the nuisance is treated as if it could be formally banished.
The flies’ reported death by morning completes the tale as a visible answer to the saint’s command. The story does not explain what physically killed them; its point is the dramatic sequence of disturbance, pronouncement, and apparent relief.
A small pest becomes a test of authority
A swarm in a chapel was more than an irritation during worship. It could disrupt prayer and make a sacred interior feel overrun. By turning the problem into a contest settled through religious authority, the legend makes Bernard’s power seem to reach even the smallest and most unruly intruders.
That is why the episode is memorable: a grave church penalty, normally associated with people, becomes the weapon in a story about flies. The chapel is restored not through a battle with the swarm, but through a sentence—and, by the next morning, the flies are said to be dead.
