How long do glow worms glow for?

What powers the light and how long can they keep it up?
05 November 2019





How long do glow worms glow for, and can they do so indefinitely?


Animal expert Sophie Mowles from ARU took on this question from NeilEP on our forum... 

Sophie Mowles - Okay. Glow worms are really interesting! They're actually a beetle and we get them in the UK and it's the female that does the glowing. So she doesn't transform in a typical way into an adult; she looks a lot like a larva but a heavily armed sort of "trilobite-type" creature about two and a half centimetres long, and she produces a glow. The male looks like a typical beetle and he's attracted to her so he'll fly through the night and and be drawn in by her glow.

Now, she produces a chemical called luciferin, which is fantastic: in reaction with oxygen, this produces a glow - so what we call 'bioluminescence' - biologically produced light.

Glow worms don't actually feed as an adult, so they metamorphose into that adult form and they don't have mouth parts. They do not need to eat at this point, all they need to do is find a mate, and mate with one another. So she's kind of stuck, she's relying on reserves that she's built up as a larva; she lived for about two years as a larva actually, eating, to make sure she's got enough reserves to produce this chemical reaction. Once she's mated, that's it - that's all she needed. So she will use his sperm and fertilise her eggs and she will stop glowing she doesn't need to anymore.

She will hopefully find a mate; if not, she might run out of energy and she might have to stop glowing. But the males, back on the subject of eggs, they really like females that are glowing strongly, because they're big they contain lots of eggs! So he's going to get lots and lots of offspring!

Chris Smith - and that's a sign if they if they can afford to glow very brightly they're well-fed: lots of energy, probably a healthy female isn't it more likely to have healthy offspring?

Sophie Mowles - Indeed, and also generally a bit larger. So her - what they call the lantern, which is the section of her abdomen that glows - will be bigger on a bigger female, and bigger female, bigger body, lots of eggs. So the males like that!

Chis Smith - Thank you very much Sophie. So there we go shedding some light on how glow worms ones work!


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