A glowing mushroom lights up to attract insects that can spread its spores, a study suggests.

The eerie green glow of the Brazilian forest fungus, Neonothopanus gardneri, fulfils a similar function as the petals of colourful flowers, scientists believe.

The discovery could solve a mystery that dates back to ancient Greece more than 2,000 years ago.

Around 71 of the more than 100,000 described fungal species produce a green light.

The Greek philosopher Aristotle noted the phenomenon and was the first person to question why it occurred.

Until now researchers had thought the effect was a simple by-product of metabolism.

But the new evidence, published in the journal Current Biology, shows that at least in the case of N. gardneri there is more to it than that.

The mushroom’s bioluminescence seems to be controlled by a circadian (day-and-night) clock, so that it only turns on its glow at certain times, thereby saving energy.

Having such a degree of regulation indicates that the green glow is there for a reason.

“It appears that fungi make light so they are noticed by insects who can help the fungus colonise new habitats,” said lead researcher Cassius Stevani, from Brazil’s Instituto de Quimica-Universidade de Sao Paulo.

To investigate the purpose of the glow, the researchers made sticky fake mushrooms out of acrylic resin and lit some from the inside with green LED lights.

Placed in the forest where the real mushrooms were found, the luminous fake fungi attracted far more beetles, flies, wasps, ants and other bugs than those that were not lit.