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)

Christine Young

Lion

Great spotting of a very impressive spider! And, the web looks blue, doesn't it? Posted 8 months ago
1. Ferdy Christant
  
  Lion
  
  It does look like it from the photo, but it's just white in reality. It's probably a color shift from cold flash light exaggerated by some post processing I did, as an unintentional side effect. A technique I commonly use is "Darken/lighten center". When a background has lots of distracting and useless details, you can emphasize focus on the main subject and it kind of "dims" the rest. Doesn't work in all scenes. Posted 8 months ago
2. 1. Christine Young
    
    Lion
    
    Ah, well, white or blue, the web is still completely awesome! Posted 8 months ago
  2. 1. Ferdy Christant
      
      Lion
      
      I find it most amazing how it doesn't get tangled up. I mean, I assume it's very sticky. How do you fold something sticky into something as small as that, and it not getting intertwined, stuck, etc? Posted 8 months ago
    2. 1. Christine Young
        
        Lion
        
        Yes! That is such a fascinating thing to consider. I sort of know the answer, although I don’t know if the same applies to net-casting spiders. Spiders can make sticky and non-sticky silk and they purposely place the sticky silk in spots on the web where they are less likely to tread themselves. Silk can also vary in stretchiness and strength. Plus, spiders have tiny barbs and bristles on their feet, so if they happen to step in a sticky spot, their fancy feet are easily freed. Also, if you think about it, a spider getting its leg stuck in its web would be much easier to free than an entire bug that has flown into the web and is now completely covered by sticky goo. The prey just can’t escape before the spider moves in for the kill because too much of their body’s surface area is stuck in the web. Makes sense, right? So, maybe net-casting spiders don’t touch the sticky parts of their webs, or maybe they do just grasp the edges of the sticky threads with their claws, enabling a quick release, if needed?
        
        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 8 months ago
      2. Ruth Spigelman
        
        Lion
        
        In all my years living here and the Deinopis I've come across - I've never noticed these aiming targets Christine. How fascinating and I'll be sure to look for that at the next opportunity, thank you. Posted 8 months ago
        
        Christine Young
        
        Lion
        
        @Ruth, you're welcome and I hope you get to observe the spots the next time you see one of these beauties!
        
        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 8 months ago
        
        Ferdy Christant
        
        Lion
        
        This is starting to make a lot more sense. If you look at that video, it always seemed to me from the speed of the bug flying at it, it's physically impossible to respond that quickly. The "early" detection system explains how it can be done, thanks for the info! Posted 8 months ago
        
        Christine Young
        
        Lion
        
        Totally awesome, right?! Posted 8 months ago
        
        Ferdy Christant
        
        Lion
        
        omg like laser movement detectors?
        
        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 8 months ago

Ruth Spigelman

Lion

So glad you came across a Deinopis Ferdy! Posted 8 months ago
1. Ferdy Christant
  
  Lion
  
  As am I. I've always enjoyed the Australian species with its awesome huge eyes. Now we have 2 species described, out of 51 :) Posted 8 months ago