Did you know spiders can fly?
Spiders fly without wings, using the material they are best known for making – silk. And spring is a great time to observe how young spiders begin their lives by taking to the wing on gossamer threads.
To see a small spider sail through the air on a thread of silk is surprising to most people. But spiders are adept at this method of transportation to find new homes far and wide. Along with some caterpillars, spiders “balloon” by extruding strands of silk from their spinnerets. The act of ballooning by young spiders was first observed by Aristotle and studied and reported in detail as early as 1827.
Recent research has shown that electric fields, detectable by spiders, also help them to become airborne. To do so, spiders climb to the top of plant stems or the ends of branches where they literally stand on their front legs in a posture called tiptoeing. Their ability to detect electric fields seems to elicit this behavior. As strands of silt lengthen, the combination of wind and electric fields lift them into the air.
Their travels can be as short as a few feet to flights of many miles. They may typically stay close to the ground but they have also been collected at 5 kilometers high. As such, spiders can be globe trotters, having been observed landing on ships far out to sea. Along with other wind-borne insects and plant seeds, spiders are also early colonizers of new oceanic islands.
What makes this behavior interesting is the unknown of where the wind will take them. As it turns out, most ballooning spiderlings do not survive their travels, for any number of understandable reasons. From falling to the ground in unsuitable habitats to being caught in the air by birds, this method of dispersion seems like throwing caution to the wind. But walking will not get a spider far and the rewards of finding a suitable new home by ballooning help species spread and survive.
As for being lifted high into the atmosphere, where temperatures drop below freezing, spiders and small insects have a way to survive the trip. The key is the antifreeze properties of the blood of these organisms that prevent cell damage. Ice does not form in their bodies, which if it did, would kill them. As a young student of biology, I was fascinated to learn about the many small insects and other invertebrates that are carried high into our atmosphere and transported to faraway places. Detailed studies conducted in the 1920s and 30s found that 1 in 17 invertebrates found at high altitudes were spiders.
What makes spiders stand out among these high-altitude travelers is the way they get aloft – their gossamer threads. As any search for this term will find, gossamer is a noun that defines the fine threads, spun by spiders to form webs or the threads that allow them to fly. So next time you see a spider floating by on its gossamer threads, wish it luck! Thanks to my friend Nancy Madden for inspiring this story.
To read another interesting article about spiders ballooning, check out this PBS Newshour story from 2018.
Hope to see you in our great outdoors!
