Science for Artists

Inspiration and Truth

Like Moths to a Flame

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go pieces arranged in a pattern painting by Katarina Countiss

go pieces arranged in a pattern

Painting by Katarina Countiss

Excerpt from The Art Instinct: Beauty, Pleasure, & Human Evolution by Dutton, Denis (Book – 2009) page 102

[To borrow a charming analogy] from Eckart Voland…With the arts, perhaps we should regard ourselves like the moths who have succeed in inventing a lantern in order to have fun circling it. If the arts are like the lantern, the Darwinian question is why we worked so hard to invent them and why we have such fun circling them in the first place. The evolved adaptations are there to be discovered, and so are their extensions into our artistic and aesthetic lives.

Excerpt from The God Delusion by Dawkins, Richard (Book – 2006) page 172-173

Moths fly into the candle flame, and it doesn’t look like an accident. They go out of their way to make a burnt offering of themselves. We could label it “self-immolation behavior” and, under that provocative name, wonder how on earth natural selection could favour it. My point is that we must rewrite the question before we can even attempt an intelligent answer. It isn’t suicide. Apparent suicide emerges as an inadvertent side-effect or by-product of something else. A by-product of… what? Well, he’s one possibility, which will serve to make the point.

Artificial light is a recent arrival on the night scene. Until recently, the only night lights on view were the moon and the stars. They are at optical infinity, so rays coming from them are parallel. This fits them for use as compasses. Insects are known to use celestial objects such as the sun and the moon to steer accurately in a straight line, and they can use the same compass, with reversed sign, for returning home after a foray. The insect nervous system is adept at setting up a temporary rule of thumb of this kind: “Steer a course such that the light rays hit your eye at an angle of 30 degrees.” Since insects have compound eyes (with straight tubes or light guides radiating out from the centre of the eye like the spines of a hedgehog), this might amount in practice to something as simple as keeping the light in one particular tube or ommatidium.

But the light compass relies critically on the celestial object being at optical infinity. If it isn’t, the rays are not parallel but diverge like the spokes of a wheel. A nervous system applying a 30-degree (or any acute angle) rule of thumb to a nearby candle, as though it the moon at optical infinity, will steer the moth, via a spiral trajectory into the flame. Draw it out for yourself, using some particular acute angle such as 30 degrees, and you’ll produce an elegant logarithmic spiral into the candle.

Though fatal in this particular circumstance, the moth’s rule of thumb is still, on average, a good one because, for a moth, sightings of candles are rare compared with sightings of the moon. We don’t notice the hundreds of moths that are silently and effectively steering by the moon or a bright star, or even the glow from a distant city. We only see moths wheeling into our candle, and we ask the wrong question: Why are all these moths committing suicide? Instead we should ask why they have nervous systems that steer by maintaining a fixed angle to light rays, a tactic that we notice only where it goes wrong. When the question is rephrased, the mystery evaporates. It was never right to call it suicide. It is a misfiring byproduct of a normally useful compass.

Author: KC

I am Katarina Countiss, a multimedia designer. I like blogs, games, art and technology. I am curious about how things are made.

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