Checking out nature’s web sites
IN an announcement about the opening of the Spider Pavilion at the Natural History Museum of Los Angeles County, I recently referred to spiders as insects. It brought this response from a reader in Whittier: “Spiders are not insects! Insects have six legs.”
The reader is correct. Spiders have eight legs. Although insects and spiders are both arthropods, spiders belong to a distinct class, Arachnida. Unfortunately, the term became known almost exclusively as a root for a word concerning the pathological fear of spiders: arachnophobia.
If you know a sufferer, pass the Valium, because this is the season for arachnophiles. For a few weeks, no Angeleno need go to a museum to see one of the great wonders of nature. Our gardens will be jumping with arachnids. Even seldom-spotted spiders will be tossing draglines across walkways and dangling at face-height in search of their last big fat fly of the season. The orb weavers of the Los Angeles Basin will be spinning their last and most glorious webs of the year.
Spiders are so conspicuous in autumn that far and away the most calls that entomologists get concern them, says James Hogue, collections manager for the biology department at Cal State Northridge and one of the region’s most respected entomologists. The sheer volume at the Natural History Museum was one of the things that gave Brian Brown, curator of the entomology section there, the idea of conducting an area-wide spider survey. Homeowners could collect spiders, send them in to the museum and, for the first time, scientists would get a picture of the most frequently spotted spiders in the L.A. area.
For the four years of the study, it has fallen largely to the museum’s arachnid specialist, Janet Kempf, to open the post. There have been spiders in vials, spiders in alcohol, smashed spiders, live spiders crawling gratefully out of envelopes, young spiders that she took home and fed until she could identify them. So far she has cataloged 3,919 spiders and counting. Of these, 32 families and more than 175 species have emerged, she says. People collecting more than 50 spiders in their homes and gardens average 30 different species. A schoolchild in Torrance even discovered a brown widow, an African relative of our black widow.
Rather than send Kempf any of the spiders from my garden in central Los Angeles (done right, this requires capturing and killing them by popping the subjects in a jar, freezing them and dropping them in alcohol), I invited her and Hogue over to see what they could find as dawn light came glinting across dew-studded webs.
Strung across the front window was the classic circular, spoked web of a common orb weaver. The spider had retreated to the day position up at the corner, with one foot on a silk line to feel for the sudden movement of an insect landing. Neither Kempf nor Hogue needed to see the spider close up to wager that it was a member of the Neoscona genus. “You can often tell the spider by its web,” says Hogue. This one lacked the whitish zigzagging or “stabilamenta,” an insect lure that reflects ultraviolet light that would have identified it as another common genus, the Argiope, or golden orb weaver.
Although all spiders can spin, says Kempf, not all make orbs. Through the house, inside the kitchen, up in the ceiling next to the porch door, there were yellow sac spiders, Cheiracanthium mildei to arachnologists -- smart little arachnids with more random-looking webs, waiting for dusk, when flies, moths and gnats might stray inside. It can give a respectable bite if you grab or poke it, but most of us know better. Evidently yellow sacs came from Europe, probably in the furniture or plant shipments.
Sharing the ceiling with the yellow sacs were what most of us call daddy long legs, but which aren’t, says Hogue. They’re cobweb or cellar spiders, or Pholcus phalangioides, which also emigrated from Europe. Real daddy long legs, he explains, are native, and though arachnids, they are actually not spiders. They are their own order, the Opiliones. Unlike spiders, which make silk to trap prey, have fangs to bite them and venom to paralyze them, real daddies have no fangs, no venom, no silk, and they do not live in ceilings, but outside in grass, where they recycle organic matter. A smashed worm and fallen fruit is their idea of dinner. According to “Insects of the Los Angeles Basin” by Hogue’s father, Charles, we have several local genera: Protolophus singularis and Leuronychus pacificus, or, in more common terms, harvestmen or aranas patronas.
Out back, Kempf found sheet webs and faintly conical webs, and speculated that the latter were the work of a funnel weaver, or native spider, the Hololena curta. Pity that the arachnids who made them weren’t hanging out because to judge from pictures, they are Oscar-gown gorgeous, orange with what in a dress would be described as black piping. Although they will bite if “molested” (a Charles Hogue term), their chief art is avoiding us. Webs always connect to some escape chute onto the ground or into a shrub, so a gardener could go years without ever seeing one.
The red jumping spider, the Phidippus formosus, might also leave a funnel web as a retreat and place for eggs, but as curiously as Kempf was poking around in the salvia, jade, box hedge and rosemary, we couldn’t find any in webs. If they were there, they were out hunting, which they do by leaping on prey, from sometimes startling distances.
It was unrealistic to hope that we would find a lair of either of our most charismatic native arachnids, the tarantulas and trapdoor spiders. Outside specimens bought from pet shops, these are rarely found in the city. But if you’re hiking and see a burrow plugged with spider silk, it’s probably the front door of one of these super spiders.
All true spiders have silk, says Kempf, they just don’t necessarily use it to trap prey. They might swing on, or use it as spider Tupperware to wrap up and store prey, or use it to spin a shelter for the night. Spiders can even make different kinds of silk, explains Kempf: sticky for trapping, stretchy for building. Weight to volume, it’s stronger than steel, Hogue adds. The Massachusetts Institute of Technology is doing its best to match the strength of a dropline of a golden orb weaver. When it does, Kevlar will have to look to its laurels.
For the gardener, the only thing Kempf and Hogue ask us to remember about spider silk is that the webs of one of the few notably venomous local spiders, the black widow, are especially sticky.
“If you suddenly feel a really strong, sticky web, you want to remove your hand,” Hogue says.
Black widows like secluded retreats, such as under houses or in rock piles. The common sensical thing for homeowners to do when carrying out jobs in these settings is to wear gloves. If you are bitten, temporary numbness and nausea are symptoms. In severe cases, there are muscle cramps. Death is rare. If bitten and concerned, see a doctor, and try to trap the spider for identification.
Most spider bites are misdiagnosed, Hogue says. As evidence, he points to the brown recluse scare. “Doctors in emergency rooms are sure that every bite is from a brown recluse,” he says. “We don’t have brown recluses in California.” Rick Vetter, an entomologist at UC Riverside, became so tired of brown recluse scares, he published an information sheet titled, “How to Identify and Misidentify a Brown Recluse Spider,” complete with a map showing their range from Texas eastward (spiders.ucr.edu/recluseid.html).
The most common spider in Kempf’s survey, the Steatoda grossa, or false widow, has the misfortune of looking like the black widow, giving the impression that L.A. is thick with danger. It’s got the classic patent-leather finish, but unlike the real thing, it lacks the hourglass-shaped red marking on the underbelly.
Spiders are only bad news if you are, say, an aphid, or any number of largely plant-eating critters that constitute its diet. Entomologists take pains to emphasize spiders’ benefit to people, but it took crop scientists to measure this systematically. A 2003 review paper out of the University of Maine reported that in a lab study, spiders reduced 58% of aphids on winter wheat, and that as many as 1,000 insects may be present in an orb-weaver’s web at any one time.
The spider’s ultimate benefit may be in its programming. Like cats, they don’t stop hunting because they’ve eaten, but keep killing suitable prey.
So as you see the orb weavers, as big as they get, at the end of their lives after a year of trapping, mating and finally leaving egg sacs behind, consider the hundreds of flies that it has kept from your dinner, the mosquito bites it has saved you, the aphids it has gleaned from your garden. Before squashing the false widow, consider that it actually preys on black widows, according to the Woodland Park Zoo in Seattle. A bite from it is not serious, unless, of course, it is radioactive and you are Peter Parker, in which case it will turn you into Spider-Man.
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A survey with 8 legs
The Natural History Museum of Los Angeles County is in its fourth year of a region-wide spider survey. Homeowners are invited to collect spiders and send them to the museum, so that scientists can record the variety and numbers.
For the 2002 results, photographs, descriptions and instructions of how to participate in the spider survey, go to the Natural History Museum’s website: www.phorid.net/spiders. The museum’s Spider Pavilion is open through Nov. 6 at 900 Exposition Blvd., Los Angeles; (213) 763-3466; www.nhm.org.
For spider questions, contact the American Arachnological Society, www.americanarachnology.org.
Recommended reference: “Insects of the Los Angeles Basin” by Charles L. Hogue, Natural History Museum of Los Angeles County, $27.95.
Emily Green can be reached at firstname.lastname@example.org.