Spiders in the garden may provide a frightful shock for those on the phobic end of the arachnid spectrum. For the rest of us, seeing spiders indicates a healthy ecosystem with plenty of biodiversity. How do spiders help your garden and which ones should you be worried about?
What makes a spider a spider?
Spiders are not insects, even though they have exoskeletons, jointed bodies, and appendages, and they breath air. Spiders and insects are both arthropods. The difference is that spiders have six or eight eyes, eight legs, and fangs that inject venom, which insects do not. Also, spiders do not have antenna. Spiders and scorpions are both members of the arachnid class. Spiders have a more centralized nervous systems than other arthropods, and they move their limbs using hydraulic pressure, rather than muscles. The webs we see are produced from glands that make silk that is spun into threads using spinnerets. There is a wide variety of web sizes, shapes, and styles within the spider community. Below is a list of the common types of spiders found win North America:
Except for one herbivorous species that was identified in 2008, all spiders are predators. These beneficial insects hunt and feed on insects and other spiders, and some of the larger varieties hunt lizards and birds. (Yikes!) The familiar sticky webs are not the only way spiders capture their prey. Some species use a lasso, while others mimic their prey to get close enough to grab them, and others actually chase their prey down before injecting them with paralyzing venom.
After capturing a meal, spiders must inject victims with digestive enzymes, because spider guts are too narrow to process solids - they actually have filters on their faces that prevent solids from getting in! Some species of spiders form social groups of up 50,000 individuals, but most spiders are solitary. Most spiders only live for two years, but some captive species have lived as long as 25 years. According to Wikipedia, “Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females.” (Sorry guys, I couldn’t resist.) Anyway, recent research has shown that spiders eat more than insects and other spiders: many species also drink nectar! And young spiders that eat pollen have been shown to have higher survival rates! Some spiders are scavengers, eating dead insects that they find. Captive spiders have even been observed feeding on egg yolk, sausages, milk, bananas, and marmalade.
Scary looking or not, spiders help us fight many garden pests without the use of chemical pesticides. In fact, spiders are believed to be the most beneficial insect we can have in the garden! Spiders commonly eat earwigs, roaches, flies, moths, mosquitoes, aphids, caterpillars, cucumber beetles, grasshoppers and crickets, pine sawflies, redhumped caterpillars, armyworms, leafhoppers, spider mites, thrips, leaf miners, spruce budworms, tobacco budworms, sorghum midges, and fleahoppers. (It may have been easier to list what they don’t eat!) Spiders also eat other beneficial insects, but the damage they prevent far outweighs the damage they do.
Most types of spider venom are not dangerous to people, with the few exceptions listed below. In fact, research is being conducted to explore the use of spider venom as both pesticide and medicine.
While spiders are a great addition to any garden or landscape, there are a few exceptions. Black widow, recluse, and funnel spider bites can cause life-threatening reactions. That being said, only 100 deaths occurred in the 20th century due to spider bites, while 1,500 people died during the same time frame from jellyfish stings. Weird. Anyway, most spider bites are much like bee stings - they hurt like crazy, at first, and then go away. You can reduce the discomfort by cleaning the area, applying antiseptic, and then ice to the area. If unusual or severe reactions occur, get to the hospital as quickly and as safely as you can or call poison control (in California, that number is 1-800-222-1222). If you don’t have the number for Poison Control in your contacts, you should do that now. Really. I’ll wait. By the way, if you do get bit by a spider, try to capture it for identification. Your doctor will thank you.
There are very few poisonous (to people) spiders in California. These include:
If you see spiders in the garden, be glad for the help they provide. And consider this:
In the 16th century, monks would go out into forests and fields to collect spider webs to use to make gossamer canvases for religious paintings. (And we thought plastic wrap was hard to work with…)
You can grow a surprising amount of food in your own yard. Ask me how!