While spiders lack wings for traditional flight, the concept of “flying spiders” comes from a natural phenomenon called ballooning. This process allows them to travel significant distances through the air, appearing to defy gravity. In this context, “flying” refers to their ability to become airborne using natural forces.
The Truth About “Flying” Spiders
Spiders cannot fly like birds or insects because they lack wings. Instead, they use “ballooning” or “kiting” for aerial dispersal. This behavior, seen in many spider species, allows them to become airborne using air currents and electric fields. It’s a passive form of travel, where the spider becomes a passenger on the wind.
Ballooning is mainly observed in smaller spiders, especially spiderlings, but larger individuals also use this technique. This aerial journey can cover distances from a few meters to hundreds of kilometers. Spiders have even been found in atmospheric samples at altitudes of five kilometers and over oceans, far from land. This capability explains how spiders colonize isolated islands and mountaintops.
How Spiders Use Air Currents
Spider ballooning involves silk, wind, and static electricity. To begin, a spider climbs to a high point, like a twig or blade of grass, and raises its abdomen. It then releases fine silk threads from its spinnerets into the air. These threads, sometimes called gossamer, are much thinner than a human hair and can extend several feet.
As these silk strands are released, they catch air currents, lifting the spider like a parachute. Spiders also harness the Earth’s natural electric field. The atmosphere has a static electric charge, with the ground being negative and the air above positive.
Spider silk can pick up negative charges. The repulsion between the charged silk and the negatively charged surface, combined with the positively charged air, provides additional lift. Spiders have tiny sensory hairs, called trichobothria, which detect these electric fields, potentially signaling optimal takeoff conditions.
Why Spiders Disperse by Air
Ballooning is a survival strategy for many spider species. Its main purpose is to colonize new territories. By traveling through the air, spiders escape unfavorable conditions like overcrowding or limited food. This allows them to find new areas with more prey and less competition.
This travel method also helps spiders avoid ground predators and hazards. Ballooning is common for newly hatched spiderlings, enabling them to disperse from siblings and establish their own territories, reducing cannibalism risk. While landing is uncontrolled, spreading widely increases the chances of finding suitable new environments.
Addressing Common Concerns
Despite concerns about “flying spiders,” ballooning is a natural and harmless process. The spiders involved are typically very small, often spiderlings or light adults, and pose no threat to humans. Their venom, like most spiders’, is for insect prey and not dangerous to people or pets.
Encounters with many ballooning spiders, where silk webs might cover landscapes, are uncommon and temporary, lasting only a few days. These events are simply mass dispersal and do not indicate an “invasion” or aggressive behavior. Spiders engaging in ballooning focus on finding a new home, not interacting with people.