The Moth and the Candle
from the book, "Petrified Lightning"

Petrified Lightning

The Moth and the Candle

"Thus hath the candle singed the moth."

Shakespeare, The Merchant of Venice

In a scene that set the stage for the 1982 motion picture Quest for Fire, a Neanderthal man is sitting near a campfire in front of a cave. Inside the cave the rest of the tribe is asleep. His job is to keep the fire burning throughout the night, for if it were to die out they would be without their most prized possession: fire, their most effective weapon and their source of light and warmth. Although they understand its uses and how to keep a flame alive, they do not know how to start a new fire. Their only solution to being without fire is to steal it from another tribe, a most dangerous quest. As the man sits watching the fire, he is intrigued by a moth flying in rapid circles around the flames. With a fast arm maneuver, he catches and promptly eats the moth.

Had this Stone Age man waited, he would have seen the moth narrow its circles around the fire until the flames consumed it. The moth would seem to have deliberately flown into the fire. This action of the moth around a flame has been observed by people of all times, from early beings up to the present. The popular opinion is that the moth becomes so hypnotized by the dancing flames that it irresistibly flies into the fire. The tendency of moths to fly into a fire has been studied intensively by leading entomologists, who use a candle as their basic research tool—hence the common pairing of "the moth and the candle."

The moth's behavior is neither suicidal nor supernatural. Actually it is a victim of a situation that rarely arose until after humans appeared on the earth. By this time the insect had evolved a tropism (an innate tendency) that would direct it to respond to an external stimulus such as light. During the millions of years before humans started lighting campfires, the moth was rarely at risk from a source of light.

A moth in night flight will beat its wings faster when light, such as from a campfire or a candle, suddenly falls on its eyes. If the light of the campfire is off to one side, it falls more strongly on one eye than the other, and the wings on the side nearer to the bright light will tend to beat faster than those on the other side. Thus the moth flies in circles around the light source. The closer it gets to the flame the stronger the light becomes, and the faster the wings beat. The pattern of the moth's flight causes it to fly in ever—smaller circles closer and closer to the source. Inevitably it reaches the flame, and ZAP!

The moth appears to have deliberately committed suicide. But actually it is the victim of one of the mistakes that nature made in developing this tropism, for even nature could not foresee every eventuality.