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Re: bauplan convergence (spiders)



Betty,
Having collected spiders for many years, we arachnologists usually call it "ballooning". But since the silk is not lighter than air, it is really more like parachuting in a stiff wind.
However, such activity is almost always done when the spiders are small hatchlings and still light enough. When bigger they can travel short distances (like branch to branch or tree to tree) by sending out a silk line into the wind until it sticks to something, and using the line to crawl across the space.
Actually the hatchlings are probably "trying" to do what the adults do, but the silken line tangles together into a sort of parachute and the force of the wind pulls the lightweight baby from its perch and off it goes, like it or not. Of course, this is great for expanding a species range, so I presume such behavior in the hatchlings would be selected for over time.
------Ken Kinman
********************************************************
From: Betty Cunningham <bettyc@flyinggoat.com>
Reply-To: bettyc@flyinggoat.com
To: dinosaur@usc.edu
Subject: Re: bauplan convergence
Date: Thu, 08 Jun 2000 15:56:43 -0700

there are 'parasailing' spiders that travel to new locations on spider
silk used as a sail*.
Why evolve wings when you can get where you want to go with what you
have?

-Betty
*or would the term be more correctly 'flotation device'?

Dinogeorge@aol.com wrote:
(Wonder why there are no flying spiders. Maybe the insects beat them to
it?)

--
Flying Goat Graphics
http://www.flyinggoat.com
(Society of Vertebrate Paleontology member)
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