Sunday, August 1, 2010

Spiders, fierce and fabulous

Don't ignore the spiders! Never ignore the spiders! And be thankful they are small.

A beautiful Shamrock Orbweaver, Araneus trifolium, hides in the sheltered fold of a milkweed leaf. While on a recent foray into West Virginia, I stumbled into some interesting arachnids and will share a few here. The above orbweaver had recently snared a Pipevine Swallowtail, and consumed its innards. Just the dried husk of the butterfly dangled from its web, and a gust blew it off just as I was preparing to make a photo of the kill. That meal demonstrates the bulletproof constitution of these spiders. The swallowtail is rather toxic and shunned by most predators.

The ornate concentric bands of a female Spotted Orbweaver, Neoscona crucifer, web imbedded in a tangle of Great Rhododendron, Rhododendron maximum. This silken work of art is big; perhaps a foot or more across. I've tried to lighten the image and adjust the contrast so hopefully you can see the web. Spider webs can be difficult to capture with the camera on bright days.

If you come across a well-maintained orb web such as this one during the day, the spider is not likely to be ensconced in the web's center, as it probably would be after nightfall. But the chances are the owner will be hiding under a leaf at the web's perimeter, probably near the top. This Spotted Orbweaver was, and it didn't take long to find her.

Now this is very cool. Spotted Orbweavers and some other spider species rig their webs with a "signal line" during the day. This tough silken strand is attached at the web's hub, and extends like a guy wire to the spider, hidden in the foliage. She holds the line under tension, which you can see in this photo. Like a fisherman manning his pole, she extends a foreleg and waits for some hapless victim to stumble into the web. The soon to be doomed creature's struggles will telegraph vibrations up the signal line, and the spider will rush from hiding and put the coupe de grace to the prey item. This is a clever system, as it keeps her out of sight unless action is required.

Wanting to see the spider in action, I found a Harvestman ("daddy longlegs") nearby and tossed it into the web. It's struggles eventually sent the orbweaver rushing down, and it was curtains for the other arachnid. The spider rapidly wraps its prey in silk, then administers the fatal bite.

We're looking at the ventral, or underside of the orbweaver as it busily deals with the victim. It's abdomen is rather creepy - it looks like a hooded grim reaper with yellow eyes glaring.

Not far away, I found a male of the same species. It is much smaller than the female and builds a much less impressive web. Males are not likely to hunt during the day, either, and may not utilize signal lines like the females do. The female's energy requirements, especially when gravid, are far greater and that may be why they will hunt day and night.

This was one creepy-looking spider, and I was totally flummoxed as to its identity. Huge and leggy, it had made a crude tangle web on the ceiling of a sheltered sandstone overhang. The thing actually blended quite well with the irregular snarls of its web, and I wasn't even sure if it was alive at first. It was. From tip of leg to tip of leg, this beast was probably a few inches across. Believe me, if you felt a tickle on your arm and looked down to find this, you'd probably let out a squeak.

As I sometimes do when mystified as to a spider's identity, I contact the man himself, Dr. Richard Bradley. No one around here knows more than he does about arachnids, and Rich is always helpful and informative. Below is Rich's reply, and needles to say this was a new spider for me!


Nice photos!

This is a famous spider (well famous among spider people)!

It is Hypochilus thorelli, the lampshade weaver. The spider is famous because it is evidently from a very ancient lineage, and has a mixture of really bizarre features, primitive features and ordinary ones. They are fairly common in situations just like you suggest and we have only one species in the east, but there is a cluster of other species in the west (another one of those odd things). I've been looking for them in the parts of Ohio in the Allegheny Plateau, but no luck yet.
Good find!




Cathy said...

Oh! Very cool. I'd not known about that signal line. I'm relieved to hear that you, too, might fight an 'eek' response to this spider.

As interesting as I find them - and I do - I'd rather be introduced at a polite distance:-)

Julie Zickefoose said...

Don't you love knowing people who can answer any question? Ohio has great biodiversity in both creatures and naturalists. Nice post, great find! I'll be looking for lampshade weavers in our sandstone ledges now.

Marvin said...

Nice spider finds and shots, Jim, especially the Hypochilus thorelli. We have interesting spiders around our place, but none that are famous.

Wren nests in... said...

Ok, now I like spiders, love 'em (well, maybe not so much the ugly weirdly-shaped ones that have no fascinating colors or "fur"), but that last one is Creeping. Me. Out. I do believe I'd let out a squeak, a scream even, even without one landing on me.

(And it actually does look rather primitive. Interesting...)

Jim McCormac said...

Thank you all for your comments!

Yes, Julie, you are in Lampshade Weaver Central down there in the hills of Whipple - that is, if they have made it across the mighty Ohio River and are in the state. You must take the fearless CB out to search those sandstone outcrops!


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