Moths to a Flame and a Setback for Romance

Photographs and words Nick Sidle

Photograph

It has been known for a very long time that moths are drawn almost irresistibly to bright lights and the flickering fire of a candle, even if the consequences are bad or possibly fatal. A moth that strays too close to an open flame may not survive and even one which simply stays too long close to a bright light can become prey, or at the very least, is likely to end the night hungry and without a meal. None of this seems to matter and the absolute demand of the attraction is why the image of a moth held by the light has become a synonym for the hopeless and irresistible draw of absolute love even if there is no hope for a future. These beliefs and its imagery are almost universal and can be seen in Shakespeare, in the idea of being ‘fire crazy’ in Native American Navaho legend, in 13th Century Persian poetry and in the writings of Goethe as well as the Bhagavad Gita in India to name just a few of the examples from around the globe and across the centuries.

Photograph – Small Elephant Hawk Moth, Deilephilia porcellus, Glen Convinth, Inverness-shire

Whilst moths may have lived this dilemma ever since they came into the world and people may have known about it from almost as soon as they arrived, what no one has been sure of is why. There are theories and models and they are real possibilities, just not ones that have been conclusively proved. The ‘Light Compass’ concept is that when moths evolved, there really were only three sources of light they would be exposed to – the moon, the stars and any wildfires burning at night. The latter would not be common, so perhaps any losses by the moths would be accepted. The first two would be constants, always potentially there, even if the moon worked through its phases. The theory is that moths navigate by orientating themselves at a constant angle in relation to the light source. Since the light source is incredibly distant, this gives a way of progressing on a straight course except that the position of the moon and stars in the sky moves through the night, so either moths compensate for this or they move short enough distances at a time for it not to matter. What this idea then proposes is that if the light source is very close to the moth, then they can’t cope and become disorientated. It is true that when there is a full moon, there is some evidence that light attraction to other sources is reduced but it has also been pointed out that all these effects are seen and are largely similar in moths that do not move significant distances or those that do suggesting that at least any mechanism like this is not simple.

Photograph – Drinker Moth, Euthrix potatoria, Glen Convinth, Inverness-shire

Other explanations have included electromagnetic radiation from the lights and flames affecting the moths or even that the light frequencies of candles can be similar to the those associated with attractant pheromones in moths. This could be true but even if there is some suggestion that the effect is greater in males, females are definitely also affected so a more complex solution would have to be in play. Then there is the open space theory, which has moths leaving cover and then ascending in the night sky towards the brightest source of light and the Mach band hypothesis, which reverses everything by starting from the position that moths are actually trying to avoid the light but, for a close bright source, they cannot process the high contrast boundary between the light and the surrounding darkness. This could well be, moth flight paths do become erratic nearer to lights and if you look at an entomologist’s moth trap there is a very bright light to attract the moths but it then provides a dark chamber where once they have arrived, the moths settle and could be said to be trying to get away from the source. There is even the suggestion that moths fly towards light to escape danger where at least a visible light represents a gap in foliage or similar where flight might give an escape. If true, this would represent a solution that might well be worse than the problem particularly in the modern world. Perhaps the simplest explanation is that the bright artificial lights dazzle and blind the moths causing them to crash and at least not be able to leave.

Photograph – Emperor Moth, Saturna pavonina, Gleń Convinth, Inverness-shire

Enter Dr Sam Fabian from Imperial College in London and a team of researchers who may have finally made more sense of what is known, what is seen and why.

https://www.nature.com/articles/s41467-024-44785-3

Their hypothesis is that moths and other insects drawn to light in effect are not attracted to the light as the cause. Using high resolution recording, they saw that moths were not flying directly at a light but were in fact turning their upper surfaces towards the light meaning that they flew at a 90 degree angle to it. In the natural night sky, putting the moon and the stars above you like this would keep a correct right way up attitude in flight. Have a close range bright source and the moth just orbits its centre. The research showed that the apparent erratic flight near a light was in fact totally consistent with maintaining an axis of tilt where the upper surface of the insect remained towards the light. Their observations also showed the alternative explanations to be less likely than had been thought. Everything could just be that the moth loses awareness of which way is up. This research may allow the design of artificial lights that are less attractive and so less damaging to night flying insects even by something as simple as changing their wavelength.

Photograph – Purple Thorn Moth, Selenia tetralunaria, Glen Convinth, Inverness-shire

So why is all of this a setback for romance? Unfortunately, replacing ‘I am so overwhelmingly drawn by my love for you that I cannot turn away’ sounds a lot better than ‘in your presence all I can do is turn my back on you’. It’s just possible that a breakthrough in knowledge of moth behaviour and an opportunity for moth conservation may be an enormous setback for the writing of romantic poetry. So now, through evolution there might, in a few years, be more moths and fewer poets except evolution is about adaptation, the poets will probably think of something……..

Photograph – Poplar Hawk Moth, Loathe populi, Glen Convinth, Inverness-shire