A web search in the Santa Monica Mountains

Armed with small plastic vials and insect nets, a group of youngsters and some accompanying adults trudged through an area of the Santa Monica Mountains on Saturday, turning over rocks, picking through long grass and rustling bushes. They were looking for spiders.

“He’s found one!” someone yelled as 5-year-old Austin Weske showed off the first capture of the day: a dull brown creature. Researcher Anna Holden, leading the expedition, said it was a wolf spider, a species known to be a good hunter that runs along the ground in search of prey.

The humans hunting for arachnids at Paramount Ranch in Agoura Hills were helping researchers collect specimens for a census of sorts of the various spiders that inhabit the Santa Monica Mountains. They want to help ensure the species’ survival.

The survey is part of a larger study to compare spiders living in Los Angeles’ urban areas with those in the surrounding wilds. The aim is to create a database detailing the distribution and abundance of the eight-legged creatures.

“Understanding spiders allows us to better understand how our ecosystem works,” said Brian Brown, curator of entomology at the Natural History Museum of Los Angeles County, which is conducting the study.

“They are critical organisms,” added Holden, an associate researcher in the museum’s entomology section. “We want to better learn how we can preserve their habitat.”

A survey now in its eighth year has allowed researchers to learn much about spiders inhabiting urban areas.

According to Brown, about 1,500 people have submitted some 5,000 specimens thus far. They hand-delivered their finds or mailed them in using perfume bottles, food containers, empty pill vials and adhesive tape.

“We’ve got an idea of what’s in people’s backyards,” said arachnid specialist Janet Kempf, who has been leading the survey of urban spiders. “Now we’re expanding to the natural surroundings.”

On Saturday, young Austin’s discovery got the hunters on a roll.

“I’ve caught another!” shouted Louie Aldisert, 7, who excitedly explained how someone slid a piece of paper under the spider and his father, Greg, joined the team effort to trap the creature.

A chorus of “wows” rang out as Holden explained that the spider was carrying an egg case, which when hatched will produce baby spiders.

“A mama spider,” cooed Jeanette Rodriguez, 12, who also found a wolf spider with several newborns clinging to its abdomen.

Holden collected more than a dozen vials of arachnids, containing species such as wolf, crab and jumping spiders.

“What we found today was pretty special,” Holden said.

“We don’t only see what type of species they are. The fact that we found many spiders with egg cases means we are able to learn something about the timing of their life cycle.”

The spiders will be cataloged and studied alongside those collected for the urban spider survey. Those have included intriguing finds, such as the brown widow, which ancestrally hails from Africa.

Brown, the entomology curator at the Natural History Museum, said spiders are often introduced from other parts of the world, in shipments and when people travel.

And just as humans play a role in distributing spiders to various habitats, they can also play a role in helping to record and protect their existence, the researchers said.

“It is critical for us that we make this a citizens’ science project, because it’s a way for them to become aware of their environment,” Holden said.

“It’s a wake-up for those who think nature only exists in exotic places.”

ann.simmons@latimes.com