A mother firefly was taking her children for a walk near dusk, and they came to a dark  woods.  "All right, kids," she ordered, "line up, and whatever happens, don't shine your light.   There are owls in the forest and they might fly down and eat you!"

The small fireflies did as they were told, with the youngest firefly at the end of the line.  As they were moving carefully along, suddenly the mother saw a light far back.

"Stop!" she whispered.  "Who lit the light back there?"

"I did," admitted the youngster.

"You heard what I told you," scolded the mother.   "Why did you disobey?"

"Well," said the little one, "when you gotta glow, you gotta glow."