Friday, September 25, 2009

Such Tangled Webs


The handsome devil pictured above is from the genus Pholcus, commonly known as "daddy long legs," and apart from the fact that it still has all eight legs attached and unbroken, closely resembles the spider I involved in a multi-species war yesterday -- a war whose depth I did not recognize.

Before I get into the details of the vicious skirmish I provoked, I cite the following background on the Pholcus spiders:

Certain species of these seemingly benign spiders invade webs of other spiders and eat the host, the eggs or the prey. In some cases the spider vibrates the web of other spiders, mimicking the struggle of trapped prey to lure the host of the web closer. Pholcids are natural predators of the Tegenaria ... It is this competition that helps keep Tegenaria populations in check, which may be advantageous to humans who live in regions with dense hobo spider populations.
It turns out that Pholcus spiders are, themselves, rather effective spider hunters. I was not aware of this; I had believed they do nothing but wander around the lower level of my house in unsettlingly large numbers and find ways to get their comically long legs broken off.

But back to the thrilling narrative: what's a Tegeneria, you ask? And who lives in regions dense with them? How does one tell a dense spider from a smart one? Tegeneria is another genus of spider, one that includes the above-mentioned Hobo spider, a nasty little beast that's quite common here in Cascadia. Whether the individuals are dense or not, they have a dangerous bite to go along with their fearsome appearance:


The third spider in the drama is a member of one of the many species of Orb-weaver spiders, who was doing what these spiders seemingly always do: sitting in her web expectantly, looking more or less bored and hungry, not unlike this one:

Several feet away from her web, my son and I noticed another Orb-weaver who had managed to entrap a bumblebee, and after chiding that spider over the decline in bee populations and the demand that every spider should be part of the solution rather than part of the problem, I had the brilliant idea of finding something to feed to the other spider. After gathering up a moth and failing to direct its flight into her web, and after scooping up a beetle and tossing it toward -- and through -- her web, I captured a hapless Pholcus, breaking off a few of its hyper-brittle legs, and introduced it to the much larger Orb-weaver.

It was not a fair fight, and therefore not much of a fight at all. Without even pausing to bite the Pholcus, the Orb-weaver quickly encased her opponent in webbing, bit her, then backed off to allow the venom to take effect. Seconds later, a gust of wind caused the web to vibrate a little, which the Orb-weaver interpreted as more struggling from her prey and responded with another bite-and-retreat. Once the Pholcus was either dead or thoroughly paralyzed, she performed a few minor repairs to the beetle-size hole in her web and then ate -- or rather drank -- the Pholcus.

As fascinating as all this was, I now realize that I fed an Orb-weaver in a way that needlessly foreshortened the life of a Pholcus, a Pholcus that might well have grown up to eat -- or rather drink -- a Hobo spider or two. If a Hobo spider climbs into my shoe and slays me, I will have no one to blame but that goddamn Pholcus spider for being in the wrong place at the wrong time -- why wasn't it already in my lower level scouting around for other, scarier spiders, leaving behind a trail of spindly severed legs? Why so easy to capture, and so game for a fight with a larger spider it should have known better than to take on? Obviously the fault is the dead spider's.

I suppose I could blame myself for precipitating prey-predator interactions that had no real business happening, but blaming oneself for one's misdeeds is a downer, not to mention deeply anti-American.

As you can see, this story really went nowhere, but it is true, and it gave me an opportunity to post photos of spiders.

Going forward, I shall be more respectful of Pholcus in view of their spider-hunting habits, and won't make fun of them quite as much when their legs fall off.

(Hobo spider image source; Pholcus image source - via; Orb-weaver spider image source)

5 comments:

Ian McCullough said...

You should know by now that interference in markets, such as the spider predation market, only leads to unfortunate market distortions of those markets. Shame on you for shafting liberty and subsidizing the orb-weaver lobby. I'm sure you have fat donations of fine silk decorating your house from the orb-weavers.

In other news, you have a genuine spider venom expert near you: Dr. Greta Binford at Lewis and Clark. Ideally, Clan FIHD might appreciate Spider Fest (if they have it this year):
http://www.lclark.edu/college/departments/biology/binford_spider_lab/public_outreach/

Dale said...

Thanks, Ian! I'm sad to report, though, that I'm the only spider fan at chez moi. The wife and the kid have no use for them, but consider them "gross" and "scary" and "disgusting" and such. I keep telling them: of course they are! Especially when one crawls across your face in the black of night! But that's a big part of what makes them awesome.

It's not the only thing that makes them awesome, of course.

I had hoped for a spider battle, even though at the time of the staging I was ignorant of phlocus's spider-killing pedigree. I knew it was smaller and destined to lose; maybe it wasn't quite so destined as I thought.

But it did lose, and not just a few of its legs.

Dale said...

And BTW, yes, it definitely proves yet again the folly of getting in the way of any market, no matter what. Never. Never! [slapping own hand]

J. Carter Wood said...

A finer example of why the Federation developed the Prime Directive is hard to imagine.

I hope you've learned your lesson, cadet.

Ian McCullough said...

Dale, you must try out the Wii game "Deadly Creatures" - it is a video game simulation of spider battling. This is actually the only game that makes me long for a Wii. http://en.wikipedia.org/wiki/Deadly_Creatures