Whenever I’m stuck for an animal to blog about, I just look up spiders. There’s never a shortage of amazing species that do crazy cool things. So today I get to tell you about the rufous net-casting spider. Presumably the first part of the spider’s name has to do with its discoverer or something similar, and the second part is pretty self explanatory.
So yes, these spiders cast nets. It’s pretty amazing, and there are some important factors that make this behaviour possible. The rufous spider’s entire life style has evolved around this net-casting ability. The spider’s body is elongated, with enormously long legs that help it make and launch its net. Its long body helps the rufous spider camouflage during the day, when it pretends to be a stick among the foliage in which it lives. Here’s a picture of this strange looking animal:
The second key to the rufous spider’s hunting success it its eyesight. An alternate name for this little fella is the ogre-faced spider, because two of its eyes face forward and are very large. Although I’m sure the rufous spider hates being called that, those eyes are critical for hunting success. The rufous spider hunts at night, and hunts entirely by sight. So its eyes have to be pretty good at seeing in the dark, and they are. They can use available light more efficiently than a cat or even an owl. This light is focussed onto a disposable membrane in the animal’s retina, which is destroyed at dawn and remade at night. Presumably this is to prevent the spider from being blinded during the day, but I might be wrong on that.
And lastly, the rufous spider has special silk from which to construct its net. Unlike most spider silk, this stuff isn’t sticky. Instead, it has a more wool-like texture, perfect for entangling insects with hairy legs. And even more importantly, the silk is super stretchy.
Now we have all the parts that make the rufous spider’s hunting technique viable; so what does it actually do? First, they wait until nightfall. Then the spiders build a pretty little net out of their special woollen thread. The spiders do this above a leaf, or tree trunk, wherever an unsuspecting bug is likely to crawl. The rufous spider then puts little white spots of faeces on the net, as aiming points. Its setup complete, the spider hangs head down from some strands of normal spider silk, holding the net open with its very long forelegs.
Then the spider waits. Once a bug crosses over one of the spider’s aiming points, the waiting ends and the spider launches itself as the insect, stretching the net to three times its original size as it does so. As the net lands on the insect, it is entangled and the rufous spider quickly bites its catch and then wraps it up. A very cool video of this whole process is shown here:
The rufous net-casting spider is really an incredible animal. It has a unique style of hunting, and has evolved every part of its life to accommodate this. Such a creative and interesting hunting technique seems almost too weird to be true, but I swear this is for real.
Cover image By Stu’s Images, CC BY-SA 3.0