“Insects are very fecund, and they would take over the world if it wasn’t for things that eat them,” Dr. Chris Barnhart, professor of Biology at Missouri State University told Ozarks Farm & Neighbor. “Spiders are the primary invertebrate predators, apart from other insects.”
When it comes to spiders, everybody knows – or should know – which ones to avoid. Those would be the brown recluse (Loxosceles reclusa) and the black widow (Latrodectus mactans et al), said Dr. Gus Lorenz, University of Arkansas Extension Entomologist. “They’re often encountered in places with infrequent human traffic. “They don’t call them ‘recluse’ for nothing,” he said. “If you’ve got a cabin up on the lake that you’re not in all the time, those are the kind of situations where brown recluses can really build up into some pretty good numbers,” said Lorenz. “When you start seeing them out and about you know that you’ve got a problem, because that usually indicates there are pretty high numbers.”
They’re easy to identify; the brown recluse has a distinctive fiddle-shaped marking on its back. Lorenz has spotted them this spring in his home and garage, and didn’t waste much time taking care of the problem. “Any of the cypermethrin or pyrethroid based insecticides for inside the home are all very effective,” Lorenz said. “Just look on the label, and make sure that it specifies spiders that it controls.”
While the brown recluse injects a hemotoxin that injures the skin, the black widow’s poison is a neurotoxin and can be extremely dangerous. Lorenz said although the widow is more of an “outside” spider, they’re also found in the same places as the recluse. “It’s a very dark black color, and it’s got that red hourglass on the abdomen,” he said. “It’s really hard to miss it.”
But even if you’re an arachnophobe, Lorenz pointed out the value of spiders to agriculture as a predator of harmful bugs. “We’ve tried to document how effective they are,” he said. “They’re part of that beneficial complex of arthropods that we like to see out there in the fields working for us.”
Barnhart said the spiders people most often notice are those that are in their homes and, he laughed, are large and hairy. “The common house spider (Parasteatoda tepidariorum) is just as it’s described,” he said. “It’s quite common; it’s actually related to the black widow, but it’s not toxic, and it’s got a spherical abdomen. It builds an untidy web in the corner, pretty much like the black widow does, and catches other bugs that get into your house.” Other than the webs and the small white spots it leaves when it defecates, Barnhart said P. tepidariorum doesn’t cause much of a problem – unlike the recluse, which preys upon it. “The brown recluse is by far the most common house spider in southern Missouri,” he said
Another spider found in the home is the parson spider (Herpyllus ecclesiasticus), a small, black arachnid that has a white mark on its abdomen and looks somewhat like a wolf spider (Family Lycosidae). And another that shares the recluse’s secluded habits, but is harmless, is the nursery web spider (Family Pisauridae), which shows up in people’s summer houses or in cabins close to water. Barnhart said, “They impress because they’re large and they look a little bit, again, like a wolf spider, but they tend to be sitting around in one place, whereas wolf spiders are down in a burrow or out walking.” Both species carry their eggs in a sac made from webbing – nursery web spiders carry them in front, and wolf spiders behind – and when the eggs hatch, the female nursery web spider lives up to her name. “They have a little web that they’ve made for them,” Barnhart explained. “The babies will go sit on that web, and be protected by the female for a while.”
Among outdoor spiders, Barnhart said the tarantulas (Family Theraphosidae) get a lot of notice in the fall when the males go on their walkabout. “People see them crossing the road and they’ll pick them up” to keep as pets, he said. “Female tarantulas are better pets because they live longer, but they’re harder to come by; you have to go turn over big, flat rocks in glade areas to get a female. But they’re fairly popular pets; tropical tarantulas are often sold in pet stores, but you can go out and get your own in southern Missouri on the glades.”
