Why are moths attracted to light but they don’t fly towards the sun in the day?

You probably didn’t realise how much mystery surrounds moths. I normally consider them as annoying  insects that enjoy circling my bathroom light while I brush my teeth.

Moths’ obsession with artificial light has no proven theory. Historically, entomologists have said that moths use the moon as a point of navigation and, unfortunately, artificial lights mess up their internal compass. However, campfires, candles and torches have been around for a few hundred thousand years and many now argue that natural selection would have rooted this out long ago by burning the ones that flew into flames. So, even though the internet holds dearly to this theory, it has been thrown aside by many.My My God, Gypsy Moth by Dr. RawheaD, on Flickr

The newest moth navigation theory involves a researcher called Henry Hsiao, who tied moths to styrofoam boats. (Yes, that’s right – moth-powered Styrofoam boats.) Hsiao wanted to track if moths really did use the light for navigation. He found they didn’t and instead flew straight toward the light then circled when they got close. It’s a mystery why they do this, but it seems to refute the old ideas about using moonlight for navigation.

I realise this wasn’t the question you asked. You wanted to know why they aren’t attracted to the sun. Quite simply, it is because moths are nocturnal creatures and so are only active when it becomes dark. In fact, they are less active during full moons because it’s too bright for them. It is now believed that moths head towards light as a way to find a place to hide; at sunrise they fly in a straight line until they hit upon a nice place to slumber. And for you and me, that will probably be in the corner of the bathroom.

Answer by Matt Powell

Question from Steve Dewar via Facebook

Article by Matthew Powell

August 5, 2013

Matt is a graduate from Oxford, who is interested in the universe and has spent many a night in the bar trying to explain space to disgruntled students. Besides being the meanest ukulele player to grace the English countryside, Matt spends his time reading, writing and walking. He’s also the intern…

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