
Deinopis madagascariensis - front view, Andasibe, Madagascar
I was thrilled to come across this awesome spider during a night tour in Andasibe. Net-casting spiders have a highly specialized and skillful way to catch prey. Instead of spinning a large cog web, they produce a tiny net-like web which they "hand hold" with their front legs. The spider has highly adapted vision to not just see in poor light, also to do so in a very wide angle. When a victim approaches the web, the spider will stretch out the net and cast it on its victim.
An unusual and impressive strategy, but it becomes even more amazing when you realize the speed and timing of it. This is a millisecond operation:
comments (12)
One other cool thing about net-casting spiders is they create aiming targets on the vegetation that they hang above. They make these targets with splashes of white fecal matter. So, when an insect crosses these aiming points, the spider knows to cast the web. Posted 3 years ago
I was dying to know more about the web and sticky issues, and so I did a bit of reading...
"With those in place, the spider then weaves another net on its front forelimbs. This stretchy net isn’t sticky, but contains threads that will entangle its victims. The net construction is loosely “web” shaped, but, at this stage, it looks more like the spider is holding a plastic grocery bag.
After completing that construction, the Common Net-Caster retreats up its safety line where it waits for prey to pass underneath. Though these spiders have great night vision, they have also learned to set up an amazing targeting system that appears to help them sense prey.
Scientists believe the targeting system works like this: First, they build their trap above a flat, uniformly colored surface, such as a leaf. As they begin construction, they put a few dabs of a white substance leaf below them. The spider uses those white dots to help it aim – when a bug blocks out the target-dots, the spider knows to launch its attack. Not before, not after, but only when the bug crosses the dots!
As the ogre-faced spider drops on its prey, it quickly stretches the net taut – an action that makes the net now look vastly more weblike. As a result, the web is finally ready for business! While plummeting toward the target spots, the spider throws the web over the bug and in a lightning-quick action, snaps it closed, trapping its prey. From there, the spider does what every other spider does – it injects it with venom and wraps up its midnight snack."
So, now we know! The little net is NOT sticky, just stretchy! So cool!
http://www.saferbrand.com/advice/insect-library/insect-education/ogre-faced-spider Posted 3 years ago
Seriously, I misread that part in my own reading. I read it as the aiming target being on the web itself so that the spider only sees a few bright points on the web itself. Posted 3 years ago