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Spectacular swarms

Duration: 03:09

A few days after each new moon during the northern winter months, spiral clouds build up above the lake surface. This strange phenomenon consists of vast numbers of tiny midges. There may be more midges in a single cloud, than there are humans on Earth. Absorbed in their dance, the midge clouds drift towards land where plants along the shore provide a resting place after hours of constant flight. But these plants hide a lot of enemies: spiders live along the lake margins in huge mixed colonies. Some spiders trap the midges in sticky webs, others use goggle eyes to stalk their quarry and pounce like miniature tigers. In spite of countless casualties along the way, the majority of the insects eventually return to the lake to fulfil their destiny. The females lay their eggs on the water surface, then die. These eggs then sink and hatch into translucent aquatic larvae, tiny predators which specialize in feeding on lake plankton. Enriched with minerals from the surrounding volcanic rocks, Lake Malawi’s waters support an abundance of plankton, which is why the midges are here in such spectacular numbers.

Available since: Tue 26 Jan 2010

Credits

Narrator
Hugh Quarshie
Producer
Phil Chapman
Executive Producer
Mike Gunton

This clip is from

The Great Rift: Africa's Wild Heart Water

2/3 Looking at the colourful wildlife of East Africa's lakes and rivers.

First broadcast: 31 Jan 2010

Image for Water Not currently available on BBC iPlayer

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