Your Friendly Neighborhood Spider

Calling all Southern California spiders: The Natural History Museum wants you.

The museum is launching its first spider survey--one of only a handful in the world to concentrate on city-dwelling spiders.

“Most people, when they make spider collections, go to natural areas where they expect to find huge spider diversity,” said Brian Brown, an associate curator of entomology at the L.A. County museum and lead researcher of the Los Angeles Spider Survey. “This is intended to be an urban spider survey. We want to see the spiders that interact with people.”

Some 35,000 species of spiders have been identified. No one knows how many may exist in the greater Los Angeles area. One estimate is about 200, but that’s a very rough guess, Brown said. He and his colleagues want to find out.

“Spiders, like most small animals, are poorly known,” Brown said. “Even in well-known parts of the world like L.A.”

Since just three people are conducting the survey, the museum is asking the public to carefully collect spiders and bring them in to be counted.

“We can’t go into everyone’s house in the L.A. Basin--as much as we would like to--so we’re asking them to collect spiders from their own homes and yards,” Brown said.

“We hope we are going to get a lot of spiders,” Brown said. “To do the job right, we need thousands.”

They should not be hard to find. Although one study on the East Coast found 2 million spiders per acre, an average Los Angeles yard contains more than 100 spiders, said Brown. These include the common jumping spider, an especially cute arachnid hunter with huge, wandering eyes.

“They’ll sit and look at you,” said Jan Kempf, a volunteer with the survey. “You can watch them watching you.”

Some of the biggest and most colorful spiders of the region are the golden orb weaver, an inch-long yellow-and-black spider that spins a web that’s 3 feet across, and the green lynx spider, with a big green-and-white abdomen.

Survey team members said they would not be surprised if their work turns up new species that have not been described before.

Almost all local spiders are harmless to people: They don’t tend to bite and usually can’t even pierce skin. But many spiders are excellent hunters.

The crab spider, which comes in bright yellow and pink, lies camouflaged within flowers, waiting to ambush nectar-seeking insects. Other spiders spit out silk to ensnare their prey or hold web between their legs and throw it over prey like a net. Still others prey on fellow spiders by pretending to be looking for a mate. And some small spiders live unnoticed in the webs of larger spiders, feeding off crumbs and leftovers.

Spiders use venom to immobilize and liquefy the insides of their prey. They then slurp up this “insect milkshake.”

The venom from most spiders is harmless to humans. The only two spiders in our area that are known to be dangerous are the black widow and the violin spider, a half-inch-long brown spider that is very rare and has so far been found only in some parts of Sierra Madre.

Despite their portrayal in the new “Spider-Man” movie, “a spider is not aggressive and doesn’t seek to bite you,” said Vygandas Relys, a spider expert from Lithuania and visiting curator at the museum who is helping to run the survey.

“You’re not a good food source,” added Kempf. “They don’t want to waste their venom on you.”

Much of the confusion about the state of the local spider population exists because spiders have not been collected extensively here for several decades. In that same time, the human population has boomed.

“We don’t know what the situation [for spiders] is now,” Relys said. While spiders are mostly harmless to people, the reverse is not true. Urban sprawl has taken away much of the habitat used by local spiders. One reason for the survey is to assess how urban spiders are faring compared to their relatives in areas protected from development.

One species particularly hard hit is the California trapdoor spider--an arachnid engineer that digs out a 6- to 10-inch burrow using sharp spines on its legs and caps it with a tight-fitting hinged lid, or trapdoor. The spiders, once common in Southern California, are now a rarity. They favor the same locales favored by developers: sunny, south-facing hillside slopes.

Ubiquitous sprinkler systems also are a problem. “Native spiders aren’t used to all that water,” Brown said.

Well-kept yards are also to blame. “If you have aggressive gardening, if you’re raking up leaf litter, cleaning up under pots, trimming hedges, you’re taking away habitat for spiders,” Kempf said.

The region’s noise pollution--from cars, helicopters and leaf blowers--also takes a toll. “Spiders use vibrations to catch information about prey and predators,” Relys said. “A lot of traffic and noise makes it very difficult for them to survive.”

Spiders are not so different from humans when it comes to immigrating and taking up life in a new country. If they are like other insects who take advantage of populated and disturbed environments, a number of new species have invaded and possibly displaced, or even eaten, native spiders.

“L.A. is an international port with goods and people coming in from all over the world,” Brown said. “We have a constant stream of spiders being introduced.”