0:00

A wolf spider pair frisks about among the dirt clods of a village garden. This mating behavior is a sure sign of spring. The wolf spider is a solitary hunter most of the year. And another wolf spider could be a dangerous adversary.

0:23

Even now, "togetherness" for this fierce predator may be little more than a wary jockeying for sex. But any spider must do whatever it takes to satisfy the urges of its kind. So, fatal confrontation is possible -- though not usual -- in this apparently romantic rendezvous. For the wolf spider -- and many of its cousins -- survival seems never more than a misstep away from violent death.

0:54

And yet, spiders have powerful tools -- and a powerful if unwitting ally -- to assure many local species, at any rate, thrive.

1:06

"People always talk about the extrasensory perceptive world of a cat or a dog in terms of smells, how they visualize their world, but all spiders live in an extrasensory perceptive vibration world. And they have hundreds and hundreds of hairs on their legs that pick up vibrations of all different sorts of amplitudes and frequency."

1:28

Dr. Andy Moldenke of Oregon State University is an entomologist. He studies arachnids' battle for life -- a battle often fought in the dark and mainly uninspected reaches of our homes. Wolf spiders are thought to invade the alien universe of carpet, bathroom tiles, wallpaper, only in search of a mate.

1:51

But Moldenke has learned certain common spider species adapted to humans over maybe thousands of years of cohabitation.

2:02

"This is a sac spider. This is another introduced spider from Europe. And this is one of the very few spiders that can cause damage with its bite."

2:16

Like the wolf spider, the sac spider is a hunter. It prowls alone. And it relies on speed and aggression to subdue insects.

2:27

But preference for the temperate climate indoors makes the sac spider a frequent, unwelcome roommate of Pacific Northwesterners. Like an overnight camper, the sac spider spins a nightly web and bivouacs on our ceilings and walls -- wherever it can go unnoticed.

2:47

"He's making a tent around him that you would have to cut your way through if you were a predator."

2:55

Sac spider venom is very toxic to humans. If its fangs were more efficient than the tiny stubs they are ... sac spiders could make our home life truly hazardous.

3:06

"The venom of the sac spider is so powerful that when it bites you, your body or your antibody responses recognizes that that is a very, very serious toxin and it will not allow it access to your bloodstream or any other part of your body. So it immediately shuts down all the capillary beds that go to that area -- completely shuts it off -- so all of the tissue, the skin tissue next to where you're bitten, dies."

3:43

Probably, sac spiders and other house spiders became tenants of the caveman in Western Europe, then crossed the Atlantic with white settlers. But the high-tech present is no barrier for the most adapted of house spiders.

4:00

"He's cleaning the tips of the legs and that's very important for the sac spider because sac spiders have the ability to walk on glass, on very smooth surfaces, just like a housefly."

4:16

Cobwebs -- a nightmare for the fastidious -- mark the trail of any house spider. Rappelling rope, route marker, security blanket, territorial fence, lasso, trip wire -- for many reasons, your local spider couldn't get along without them.

4:35

"And those are the spigots out of which the liquid silk is secreted and as soon as it hits the oxygen it turns to a solid. And any spider has maybe a half-dozen different kinds of spinnerets for secreting different kinds of silk, whether it's sticky, whether it's not, whether it's elastic, whether it's not."

4:56

Andy Moldenke believes any house harbors vast numbers of insects. And, so, the opportunities indoors are limitless for spiders.

5:07

Watch this orb spider work. The window is a hatchwork of spider silk tripwires. They were laid down by a cobweb spider that has left the scene. But the orb spider is extremely sensitive to vibration. It will be alerted to the presence of this leafhopper the instant it brushes against a silken strand. The spider's is a hair-trigger reaction.

5:37

Watch it again. The video camera shoots 30 frames a second. But the orb spider is faster still. Here the bug has yet to brush the silk and trigger a response. In the very next frame -- the spider is moving so fast the camera captures nothing but a blur.

6:00

"It takes the tip of the leg and puts it in the drop of liquid silk as it leaves the body, and draws it out, exposes it to the oxygen, to make it into the silk."

6:10

But demonstrations of ferocity aren't the whole story, Andy Moldenke says. Here in the basement rafters is evidence of spider domestic life. The discarded skins of young long-legged spiders grown to adolescence and independence hang like playsuits in the closet. The mother cared for its young much as any bird might have done. "Any prey that she catches during that time, once she digests it, she will then regurgitate and feed each one of the babies, the same as a mother bird would do."

6:47

And yet, in a spider's world, despite razor-sharp instincts and the advantages of human shelter, there seems little certainty.

6:57

Our orb spider has terrible eyesight and misses a meal right in front of its face.

7:02

And the maternal instinct has distinct limits -- as this juvenile long-legged spider learns too late.

7:10

"It may be such a young spider that it still expected its mother spider to catch prey and feed it. But it blew it, big time. The maternal instinct is only activated hormonally for a certain period of time. It protects babies from predators, you name it. But after a certain period of time, whatever the cue is, that hormone shuts off. And it's time for those babies to move on. And if they don't, they probably end up as food."

7:42

A human dwelling through spider eyes is jungle-like. Survival is an open question. Central heating has sucked the humidity from the air indoors, turning the modern house into a desert. House spiders trapped in your sink and bathtub are looking for water.

8:02

And some spider survival tricks may be a measure of the terrific strain of staying alive -- even under a roof.

8:11

"They will frequently eat that web to regain all that protein in their body and then once they move to a new site, that same protein has been converted into amino acids, and then goes to the spinnerets, is turned into silk again, then put in a web at a new site."

8:27

Depending on the species, a female house spider will lay between 24 and 200 eggs. Only one or two of those offspring will survive. Most will fall prey to ants or other spiders.

8:43

But the long-legged spider seems to have developed a strategy to confound higher species. Frighten her and she'll turn her web into a trampoline.

8:54

"If it can surprise you by doing that, it might surprise you by doing something really nasty to you, so you just go the other way and you let it be."

9:02

House spiders must enjoy some advantage from rooming with humans or they'd leave. But spiders had millions of years adapting to unimaginable changes. Should we prove less successful than arachnids at the game of survival, they could probably learn to live without us.