New York, March 20 (IANS): Did you know that there are mushrooms that actually glow? Now researchers have found out why.

The light emitted from those fungi attracts the attention of insects, including beetles, flies, wasps and ants, says the study published in the Cell Press journal Current Biology.

Those insect visitors are apparently good for the fungi because they spread the fungal spores around.

The new study also shows that the mushrooms' bio-luminescence is under the control of the circadian clock.

In fact, it was that discovery that led the researchers to suspect that the mushrooms' light must serve some useful purpose.

"Regulation implies an adaptive function for bio-luminescence," said Jay Dunlap of the Dartmouth's Geisel School of Medicine.

"It appears that fungi make light so they are noticed by insects who can help the fungus colonise new habitats," said Cassius Stevani of Brazil's Instituto de Quimica-Universidade de Sao Paulo.

The circadian control of bio-luminescence makes the process more efficient.

There are many examples of living things that generate light in various ways. Among bio-luminescent organisms, fungi are the most rare and least well understood.

Only 71 of more than 100,000 described fungal species produce green light in a biochemical process that requires oxygen and energy.

Researchers had believed in most cases that fungi produce light round-the-clock, suggesting that perhaps it was a simple, if expensive, metabolic by-product.

The new work suggests that just isn't so.

The researchers found that the mushrooms' glow is under the control of a temperature-compensated circadian clock.

They suggest that this level of control probably helps the mushrooms save energy by turning on the light only when it's easy to see.

To find out what that green glow might do for the mushrooms, the researchers made sticky, fake mushrooms out of acrylic resin and lit some from the inside with green LED lights.

When those pretend fungi were placed in the forest where the real bio-luminescent mushrooms are found, the ones that were lit led many more staphilinid rove beetles, as well as flies, wasps, ants and true bugs to get stuck than did sticky dark mushrooms.

The findings are not only cool, they are also important in understanding how mushrooms are dispersed in the environment, the researchers said.

That's key because mushrooms such as N. gardneri play an important role in the forest ecosystem.