The rare sight was discovered by Devon Wildlife Trust officer as she walked along the River Torridge.

The mystery wildlife objects were found hanging from a tree over the River Torridge. Photos Devon Wildlife Trust.The mystery wildlife objects were found hanging from a tree over the River Torridge. Photos Devon Wildlife Trust.

A STRANGE phenomenon caused a buzz over the River Torridge when it was spotted by an officer from Devon Wildlife Trust.

Louise Davis, a water advisory officer on the Northern Devon Nature Improvement Area project, was walking along the riverside near Torrington when spotted something hanging over the water from a tree.

"It was about the size of my fist, dangling from a branch," she said.

"Then I saw several other similar shaped balls all hanging from the same tree.

"At first I thought they were just debris that had got stuck, but on taking a closer look I discovered that each was a tightly-packed dome consisting of hundreds of flies.

"I'd never seen anything like it before."

Puzzled Louise took photographs of the balls and showed them to colleagues, including Martin Harvey, a leading fly expert.

Mr Harvey revealed the mysterious object was in fact a cluster of female Atherix ibis flies which come together in the rarely-seen formation to lay their eggs.

The balls can consist of several hundred flies and often form where flood refuse has been caught in the branch.

The females lay their eggs in a glutinous gloo and die, leaving a suspended mass of dead flies and eggs.

When the eggs hatch the fly larvae drop into the river to begin the next stage of their life cycle.

Louise added: "My role for the Northern Devon Nature Improvement Area is about working with local landowners to improve the water quality of the River Torridge for the benefit of local people and wildlife.

"This means I'm outdoors a lot amongst the beautiful countryside of North Devon.

"I also get to see a lot of wonderful wildlife at close quarters, but I'd never seen anything like this. Nature really is full of surprises."