Orb Web and Funnel Web

2010 November 27

In the backyard near the strawberry patch, we have a free-standing iron plant-hanger. A tiny little yellow orb-weaver spider used it as a support for a tiny little orb web, about two inches across:

I expect it was a recently-hatched spider, with a body maybe one or two millimeters long. These pictures show the virtues of an orb web. First of all, it uses a bare minimum of silk to cover an area much bigger than the spider, and she can dash quickly to any part of it when a prey item hits it. Second, the spiral strands are sticky (so that little midges that hit them will adhere), while the straight strands running out from the center are not (so that the spider can run along them without getting stuck herself). And third, it can be really hard to see. That first picture was angled so that the light would reflect off of it, but if we change the angle just a little, it is a case of now you see it, and now you don’t:

Orb weavers in the family Araneidae all spin this characteristic web type, which makes it easy to identify them to family, but many of them are kind of nondescript and this one is so tiny that I’m not even going to make a guess at the genus. Instead, let’s compare the orb web to another fantastically common type of spider web, which is also normally almost invisible except when it is covered by the morning dew, like this one:

Funnel webs like this are characteristic of a different family, the Agelenidae,and are built in the grass, not up in the open air like orb webs. Instead of trying to catch insects as they fly along, the funnel webs are built to catch insects as they try to land. And instead of using sticky strands, they have a sheet surface that tends to tangle up the claws of insects so that they can’t release their feet immediately. So when this happens, the spider feels the vibration, and dashes out of her little funnel-hole to grab it before it can free its feet and fly off. Here she is in her hole:

That funnel extends back into the grass, so that if something like a spider-hunting wasp comes around, she can dash back into her hole and escape. It also gives her a good place to drag back her prey so she can eat it in peace.

The way these two kinds of spiders manage their webs is very different:

The orb-weaver web is a very temporary structure, that is easily damaged. And, since it has sticky fibers, it picks up dust and debris very quickly. So, every day or so the owner of the orb web will go through, eat the sticky strands, fix the long framework strands, and respin it (which takes about an hour).

On the other hand, the funnel web is more permanent. The inhabitant will keep extending and repairing it by making more silk for extended periods. Since the funnel web is not sticky, and also not intended to be so invisible, there is less need to rip it out and start over periodically.

There are other styles of webs, of course, but these are two of the ones that are most easily seen. In particular, they are usually built out where the dew will form on them during the night, making them briefly visible in the early morning just as the sun comes up.

And now, because I know you all like this sort of thing, a close-up of a funnel-weaver spider’s face[1].

You’re welcome.

[1] Remember that huge grass spider that I posted back in April? Well, she finally died (evidently of old age) on July 6. So I was able to pose her for some close-up shots of her face like this one, before Sam and I took her outside and gave her a decent burial in a teeny, tiny little grave.

9 Responses
  1. November 27, 2010

    {shudders} That funnel-weaver face looks like a woolly mammoth!

  2. Carole permalink
    November 27, 2010

    You’re so right, I did enjoy it, as well as your narrative. Thank you for taking the time to share. I wonder how long you had to wait to get a picture of the funnel-weaver in his web. I often see them popping down as I walk by but have never waited for them to come back out.

  3. November 28, 2010

    Carole: I only had to wait a couple of minutes for it to pop back out. It might have been shorter, but my fussing around to set up for a picture might have been sufficiently alarming to make it wait longer. It didn’t seem to be bothered by the camera flash, though, so as long as I didn’t move the camera around I could take pictures pretty freely.

  4. November 28, 2010

    I had no idea that the radials weren’t sticky. Another fascinating tidbit from The BAP! And yes, thank you for the face shots. I never get tired of those. The eyes make me think of this loldog.

  5. November 29, 2010

    Anne: Now that you mention it, it does kind of look like a mammoth.

    Sometimes, I’m sad that mammoths and mastodons no longer roam about in Michigan. But then, I think about all the troubles I have with deer eating our crops, and consider what it would be like to have a couple of mammoths come tearing across the property. And then I figure that maybe it’s just as well.

  6. November 29, 2010

    KT: I understand that not only do the orb weaver spiders have a choice of sticky/nonsticky, they also can vary other properties like springiness and thickness. I’ve seen some claims that a single spider can produce as many as seven distinct kinds of silk.

  7. December 1, 2010

    “I’ve seen some claims that a single spider can produce as many as seven distinct kinds of silk.”

    Wow! The anatomy of the spinning portion of the spider must be really complicated.

  8. December 7, 2010

    This is a lovely photo, Tim!

  9. December 7, 2010

    Thanks, Alex!

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