Spiderling ballooning
Animal dispersal allows young or juvenile animals to seek a home in a new location where they can survive and reproduce. One type of animal dispersal becomes very noticeable during winter months. If you’ve ever noticed thousands of tiny silk threads covering your school field, clinging to fence lines or drifting in the breeze, you’ve witnessed the way spiders disperse.
Spiderlings preparing to balloon
Square-ended crab spiderlings climb to the tip of a harakeke flower head in preparation to balloon.
Spiderlings use ballooning as a form of passive dispersal to find new habitats and avoid competition with siblings.
After hatching from their egg sac, tiny baby spiders – called spiderlings – climb to a high point such as the top of a blade of grass or a shrub. There, they drop a silken anchor thread to keep themselves safely attached, then raise their front legs into the air. Using special fine hairs on their legs called trichobothria, they can sense air flow and electrical conditions in the environment.
The Earth’s atmosphere holds a positive electric charge while the Earth’s surface – and the spiderlings’ silk – hold negative electric charges. The opposite charges attract – as we see with magnets. This creates an electric field and helps the small spiderlings defy gravity and launch into the air.
If conditions are right, spiderlings will tiptoe on their back legs, point their abdomens toward the sky, and release fine threads of silk from their spinnerets. The threads form a triangular-shaped parachute that catches the breeze and uses air currents and the Earth’s electrostatic field to lift the spider into the air. With little control over where they’ll land, each ballooning flight is a leap into the unknown.
Pasture covered in ballooning threads
Silk from ballooning spiderlings covers a pasture in the Waikato area.
When hundreds or even thousands of spiderlings take off at once, the sky can fill with shimmering silk. These threads drift and tangle across the landscape, creating silken highways – a beautiful sign of mass ballooning in action.
Where do they go from here? Most spiderlings travel only a few metres, but some can float for hundreds of metres or even several kilometres. In fact, the famous scientist Charles Darwin was delighted to discover one evening that his ship, HMS Beagle, was covered in fine, silky threads. He was off the coast of Buenos Aires at the time, and those threads had floated through the air, carried by spiderlings ballooning from at least 100 km away.
Competition for food and space
This amazing behaviour happens because spiders need to move away from where they hatch. A single spider egg sac can contain hundreds – or even thousands – of eggs. That’s a lot of siblings all in one place, competing for the same food and space. To give themselves the best chance of survival, spiderlings spread out to find new habitats and avoid competing with their brothers and sisters.
Silk threads on the fence and grass
The silk threads are evidence of the many thousands of spiderlings that have hatched and migrated in this single location.
Scientists still have a lot to learn about which spiders use ballooning behaviour, especially in Aotearoa New Zealand. In other parts of the world, studies have shown that most ballooning threads belong to money spiders (Linyphiidae) – a very diverse group made up over 4,700 species globally – but many other types of spiders also use ballooning to travel. This makes it an exciting area for future research in Aotearoa New Zealand.
How does ballooning work?
For many years, scientists believed that spiderlings relied mainly on wind conditions to decide when to balloon and take flight. Initial research had found that spiderlings would only balloon when wind speeds were less than 3 metres per second. But more recent research has revealed a surprising new factor: the Earth’s electric field plays a key role in helping spiderlings lift off.
The atmosphere holds a positive electric charge, while the Earth’s surface carries a negative one. Because opposites attract, this creates an electrostatic field that points downwards. When spiderlings release silk, the threads become charged through friction – like how rubbing a balloon on your head creates static electricity. These charged threads repel each other, spreading into a fan shape that acts like a parachute. At the same time, negatively charged silk is pulled upwards by the positively charged atmosphere, creating a lift force that can carry the spiderling into the air – even when there’s no breeze. This discovery shows how science builds on earlier ideas, deepening our understanding of nature over time.
Spiderling silk in the morning fog
Spiderling silk is easy to observe on foggy mornings when moisture adheres to the threads.
Ballooning isn’t just something spiders do – other tiny creatures take to the skies this way too. Spider mites (Acari: Tetranychidae) and some moth larvae (Lepidoptera) also use silk threads to catch the wind and travel to new places. While the basic ideas are the same – using silk to create drag and lift – their method is a little different. These animals dangle from a silk thread into an open space, and when the thread breaks or is released, they’re carried away by the breeze. This variation is known as suspended ballooning, and it’s another way small creatures use silk to explore the world.
Spiderling ballooning is an example of passive dispersal. Animals that use passive dispersal do not choose where they end up. Instead, they rely on features in their environment like wind or ocean currents to disperse.
Ballooning also differs from migration, which is typically done by adults on a regular, often seasonal basis.
Up and away
Explore spiderling ballooning and animal dispersal with the activity Spider parachutes.
Related content and activity ideas
Meet the author of this article, Dr Chrissie Painting, in our All about insects webinar.
Chrissie was part of the team who developed these Buzz in the Garden activities:
Discover more of our resources on insects or explore the range of content under our invertebrates topic.
Spiderlings use Earth’s electrostatic field to aid dispersal. The article Static electricity and electrical charge has simple, effective images that illustrate this concept.
Useful links
These resources provide additional information about how spiders use electric fields in ballooning:
How spiders use electricity to fly – National Geographic video (YouTube)
Flying spiders! – BBC Earth video (YouTube)
‘Ballooning’ spiders take flight on Earth’s electric fields – The Guardian
Research sheds light on mystery of how spiders ‘take flight’ – The Guardian
How spiders use electricity to fly – New Zealand Geographic
These articles look at spider ballooning events in Aotearoa New Zealand:
‘Ballooning’ spiders behind giant webs blanketing Napier parks and grassy areas – Stuff
Giant webs as spiders ride silk parachutes, lay down safety lines to escape floods – Stuff
Find out more about Dr Chrissie Painting’s outreach Cultivating Connections: Lessons on Community Engagement from the Chatham Islands in this Royal Society Te Apārangi article.
Acknowledgement
This article was written by Dr Chrissie Painting, Senior Lecturer, Ecology, Biodiversity and Animal Behaviour at the University of Waikato Te Whare Wānanga o Waikato.
