Delaware spiders more friend than foe, UD experts say
9:34 a.m., Oct. 26, 2011--A big, furry, fake spider, dangling over a doorway or front porch, should produce a few screams from unsuspecting trick-or-treaters -- before they dissolve in giggles when they discover that this particular arachnid is made of plastic.
As for real spiders, people don’t have much to fear, especially here in Delaware, according to Brian Kunkel, an entomologist with University of Delaware Cooperative Extension.
Fishing, filtering, math
Most large, hairy, and scary-looking spiders, such as the wolf spider, will hurt a fly but they won’t hurt you.
“Delaware’s native spiders are more friend than foe," says Kunkel. “Only one poisonous spider is found in Delaware, the black widow. Of course, for those who are allergic, any spider bite can be a problem."
Spiders are considered beneficial because they keep insect populations in check. Insects and spiders are both classified as arthropods but insects have three body parts and six legs, while spiders have two body parts and eight legs. In addition, spiders have two hand-like appendages called pedipals that they use to hold food. The pedipals contain sensory organs that allow spiders to taste their food. These sensory organs also are found on the spider’s legs.
The majority of spiders have eight eyes but despite all those eyes most spiders have bad vision, says Kunkel. An exception is the jumping spider, which relies on its keen eyesight to locate its next meal. After spotting its prey, this spider takes a flying leap and, if successful, lands right on top of it. The wolf spider also captures its prey by hunting and chasing it down, though it’s more a sprinter than a jumper.
Another group of spiders captures its prey by using the ambush method – they just hang out, motionless, until a tasty little insect comes along into easy grasping range.
Constructing a web is the most common method that spiders use to capture prey. Web spinners in Delaware include the orb weaver, comb-footed, sheet web and funnel web spiders.
When it comes to dining habits, spiders are generalists, meaning they’re a lot like the guy at the smorgasbord sampling one of everything. In contrast, the monarch butterfly caterpillar is a specialist because it eats milkweed and only milkweed. If you want to attract spiders to your yard – so they’ll gobble up all the bad bugs – plant a variety of plants and plant types, says Kunkel. Use as little pesticide as possible; it can kill spiders as well as the pest insects.
“Spiders are a sign of a healthy garden,” says Kunkel. “They are often the most important biological control of pests in the home landscape as well as on cropland. In addition, spiders are a good source of food for birds and small mammals, particularly in winter and spring.”
Doug Tallamy, chair of UD’s Department of Entomology and Wildlife Ecology, can personally attest to the role of spiders in controlling pests. The first summer he lived in his house it was overrun with flies, thanks in part to a nearby horse barn.
Then Tallamy and his wife began transforming their barren yard. “When we moved in, the yard supported little more than mustard grass and ragweed,” he says.
After he planted a wide variety of native trees and plants, the wildlife came – everything from bluebirds to spiders.
“One predator, in particular, that I saw pouncing on the flies is a species of jumping spider,” says Tallamy. “These small but powerful spiders learned that our windows are great hunting grounds for flies.”
Because our trees and shrubs have grown since that first summer, the jumping spider now has plenty of places to hide and lay its eggs. And our native plantings provide an alternative food source, as well.”
So go ahead and scare someone with a fake spider this Halloween – just don’t scare off the real, beneficial spiders in your yard and garden.
Article by Margo McDonough
Photo by Evan Krape