Spiders are generally associated with dark corners. But did you know some of them can fly?
New research has been done on crab spiders that make parachutes from their webs to travel distances too great to walk. Baby crab spiders use the web technology to leave their home after hatching and adult crab spiders use their silky parachutes to more efficiently find new mates and look for food sources.
There has been documentation of some brave spiders crossing oceans with their DIY parachutes. Parachuting behavior is commonplace for crab spiders, but the exact details of how they do this feat have never been studied intently, until now.
Berlin-based aerodynamics engineer takes a closer look
An aerodynamics engineer at the Technical University of Berlin, Moonsung Cho, has taken an in-depth look at exactly how these little creatures manage this incredible feat. An average crab spider is about 5 millimeters long so a fairly decent size for a flying animal.
They worked well for the research as they were big enough to be filmed by Cho without the need for too much high tech camera equipment. Cho’s experiments with the spiders were quite simple, but it worked well to gain some really interesting insights into the way the spiders fly.
Cho gathered a sample of 14 spiders and took them to a park in Berlin and placed them on a domed sculpture to watch the way they interacted with natural winds. He had previously done studies of the creatures with wind tunnels in the lab.
He observed some common behaviors amongst the way the spiders tested the air and checked the conditions for flight. First, the eight-legged animals would lay down a silk anchor strand, then they would reach up in the air to test the wind conditions.
Spiders use front legs to analyze wind conditions
It seems, they were testing for wind velocity and direction, much like the way we lick our finger and stick it in the air. The crab spiders are looking for the perfect condition which is anything less than 3.3 meters per second with an upward draft.
Once they have found the right wind environment, the spiders then stood up very straight, stuck their rears in the air, and produced 50 to 60 nanoscale silks that lifted them into the skies. Each of these silks is nearly three meters long.
Once the silks are up, the spider lets go of their anchor strands and fly away. “You need to see it to believe it,” said Cheryl Hayashi, a spider biologist at the American Museum of Natural History.
“It gives you a deeper appreciation for how spiders have evolved to do this feat—they’re literally sailing through the air.” Cho found that this method of flight works because of the comparable thickness of the silks to the air’s viscosity.
Each of the strands produced by the spider was on average thinner than the wavelength of visible light, which ranges from 400 to 700 nanometers. “Most winged insects flap their wings to build a vortex of air to lift their bodies and make them float,” Cho told online media.
But these nanoscale silks are so thin that they use the viscosity of air to stay afloat. “From the viewpoint of spider silk, the air is like honey.”