The lower Erigone spider is in a pre-parachuting posture known as the “tip-toe” position (Image: Rothamsted Research)

The mystery of how spiders use silk “parachutes” to carry them hundreds of miles – sometimes across open ocean – may have been explained by a new model.

Spiders use simple parachutes to ride the wind wherever it may take them. The tiny creatures, weighing only a few milligrams, typically crawl up to the edge of a blade of grass, stick their backside in the air and release a thin line of silk, like that used to build their webs.

This “dragline silk” is so fine that it encounters an unusual amount of air friction and, as a result, it acts like a parachute. Each gust of wind can pull the spiders, such as Erigone atra and Tenuiphantes tenius, further into the air.


Researchers previously used mathematical models to estimate how far the spiders could travel using dragline silk. But these simulations could not explain the long distances spiders can travel: they are often the first species to colonise new volcanic islands, sometimes isolated from other land by as much as 200 miles.

Nor could the older models explain why parachuting spiders are found at remarkable heights, typically occupied by high altitude aircraft.

Silky skills

Part of the problem is that previous models do not take into account the flexibility of the spiders’ silk draglines, explains Dave Bohan of Rothamsted Research, an agricultural science institute in Harpenden, Hertfordshire, UK.

His team re-modelled the equations to take this flexibility into account. The revamped models treat the dragline similarly to a yo-yo string instead of as a fixed-length thread. And these simulations seem to match up with the long-distance reality of spider travel.

While most of this work is theoretical, the team is currently measuring the flexibility of real silk draglines. They hope to plug this real-world information into the revamped equations to calculate a limit on how far parachuting spiders can travel.

Bohan believes that understanding the way spiders can parachute into areas could one day even help reduce farmers’ pesticide use as spiders are prime predators of bugs such as aphids, which devastate food crops.

Journal reference: Biology Letters (DOI: 10.1098/rsbl.2006.0486)