With Halloween coming up I am seeing lots of scary faux spiders among front yard Halloween decorations. I must admit I am guilty of feeding into the arachnophobia that so many people have by placing a big fake hairy tarantula in my yard.
Fascinating Creatures
Most spiders are solitary creatures, but some form groups and even cooperate in brood care, caring for other spiders' offspring.
Not all spiders spin webs but those that do can create an incredible assortment of web designs, depending on the species, including spiral orbs, funnels, tubular, or ground sheets.
In some cases, two or more males will perform for a female to compete for her favor.
Some drop their silk to act as parachutes so they can drift on the slightest breeze
While spiders do not have brains in the traditional sense, a type of jumping spider appears to remember similar prey it has encountered, using trial and error to determine what works in capturing it.
Common and Beneficial
Spiders are the most common miniature living things living in our homes (besides micro-organisms). We are seldom aware of them because they conceal themselves in hidden spots (thus camouflaging themselves from their prey), tend to be active at night, and avoid humans. After all, we are much bigger than they are!
Spiders are beneficial organisms because they feed on common indoor pests such as mosquitoes, flies, roaches, earwigs, and moths. An additional benefit: many of the indoor pests that spiders consume can transmit diseases, i.e., mosquitoes, fleas, flies, and cockroaches. If left alone, spiders will consume most of the insects in your home, thus providing effective pest control.
Spider Bites
The jaws of most spiders are too small to bite humans. Of those that can bite, they will bite only if provoked, but very few spider bites are dangerous to humans. If you are bitten, the bite area may swell slightly and itch.
The adult female black widow is the primary spider in California capable of seriously injuring people. If bitten, remain calm and seek medical help.
Contrary to common myth, the brown recluse spider does not reside in California.
Managing Spiders
If you do have a spider issue around your home, the most effective way to manage them is to do regular housecleaning. Sweep or vacuum up their webs both indoors and outdoors, and prevent clutter build up that can provide hiding places for them both indoors and outdoors. If you do come across one, capture it in a jar and release it outside in an out-of-the-way spot. Avoid using pesticides since the chemicals will also kill other beneficial insects.
Appreciate Spiders Beneficial Role and Help Protect Them!
I will continue to put out my big “scary” tarantula out with the Halloween décor because spiders are so awesome. However, I do not put out the fake webbing, because like real spider webs, they can trap beneficial insects, spiders, and even small birds such as hummingbirds.
I will continue to allow spiders to share my home and garden, so they can do their crucial work of reducing pests. I much prefer having a few spiders around than mosquitoes, flies, moths, or cockroaches!
You do not have to love spiders like I do, but I hope you can appreciate the vital role arachnids play in our homes and gardens, and generally let them be.
References:
Spiders: https://ipm.ucanr.edu/QT/spiderscard.html
Pests of Homes, Structures, People and Pets: https://ipm.ucanr.edu/PMG/PESTNOTES/pn7442.html
Denise Godbout-Avant has been a UC Cooperative Extension Master Gardener since 2020.
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- Author: Denise Godbout-Avant
Why Are People Scared of Spiders?
One possible reason for people's fear of spiders is they are so different from the rest of nature, which Hollywood and the media have exploited.
Spiders are arachnids, a class of invertebrate creatures, which also includes mites, ticks and scorpions. Unlike insects, arachnids have eight or more legs, with two major body parts (insects have three), a fused head and thorax called the cephalothorax, and the abdomen.
Like mites, ticks and scorpions, most spiders are venomous, using venom to catch/kill their prey. However, the jaws of most spiders are too small to penetrate human skin. Only those spiders whose venom can cause a severe reaction are called “toxic” spiders.
Spiders in the World and California
Spiders have been around a long time – fossilized spiders have been found in 318-million-year-old rock. Today there are about 40,000 types of spiders in the world, on every continent except Antarctica. They range in size from a miniscule 0.02 inches (0.5 mm) to hairy tarantulas up to 3.5 inches (90 mm).
- California has quite a few tarantula species, none of which are venomous. They tend to be long-lived, and use silk to line their underground burrows.
- Orb weaver spiders are often large and colorful. Along with their distinctive, sizeable, elaborate webs they are easy to spot. Their venom is harmless to humans.
- Sheet web spiders are small brown spiders who build messy sheets of webbing, often on the ground. Their venom is harmless to humans.
- Cellar spiders, aka “daddy long legs” initially came from Europe, have long skinny legs, and often hang upside down. Their venom does not harm humans.
- Wolf spiders are free ranging predators who don't build webs and are harmless to humans.
Only four species of spiders in the world are really dangerous to humans: Sydney tunnel web spider (Australia), Brazilian wandering spider (Brazil), African sand spider, and widow spiders (global).
California's widow spider is the well-known adult female western Black widow (Latrodectus hesperus).
Their web is sticky, irregular and tough-stranded. During WWII widow silk was used to make the crosshairs in gunsights. Widespread in California, with as many as 20-30 per urban/suburban property, Black widows are found in the holes, crevices, trash, and clutter of human structures. Her distinctive shiny black body with a bright red hourglass on the underside of the abdomen is a warning signal to others which makes her easy to identify and thus avoid.
Misinformation on Spider Bites
Most spider bites cause no reaction or as much harm as a bee sting or mosquito bite. According to Spider Physiology and Behavior, Volume 41, there were only about 100 recorded deaths from spider bites globally during the entire 20th century! The last death by spider bite in California was in 1976 (due to septicemia). Other arthropod bites, including ticks, fleas, bees, wasps, bedbugs, mosquitoes, deer flies and horse flies, may be mistaken for spider bites.
A bite from black widow venom can cause fever, cramping muscle and joint aches, but it does not cause sores. But they are shy and reluctant to bite; when they do bite, it is often dry (no venom). On the rare occasion someone is injected with their venom, there is an effective antivenom available.
Brown Recluse Spiders
Management
Beneficial Spiders
Spiders are extremely beneficial due to being important predators of pest species. They are often the most important biological control of pests in and around homes, yards, gardens and agriculture. It is estimated that spiders eat 800 million tons of bugs a year. According to Norman Platnick of New York's American Museum of Natural History, “Spiders are primary controllers of insects. Without spiders, all of our crops would be consumed by those pests” and we could face famine.
I have always scooped up spiders I find in my home to carry them outside and will continue to do so. I am removing the spiders from my Halloween décor, since I do not want to continue misrepresenting these valuable creatures.
Resources
- UC Davis Dr. Lynn Kimsey's talk on spiders via UC IPM Urban & Community Webinars: https://www.youtube.com/watch?v=b6ExDP5wNVw
- UC IPM Natural Enemies Gallery https://www2.ipm.ucanr.edu/natural-enemies/spiders/
- UC IPM Quick Tips Card http://ipm.ucanr.edu/PMG/PESTNOTES/pn7442.html#SPIDER
- UC Riverside https://spiders.ucr.edu
- https://www.livescience.com/22122-types-of-spiders.html
- Author: Lynn S. Kimsey
- Posted by: Lauren Fordyce
Arachnophobia: Should You Be Afraid of Spiders?
Fear of spiders, arachnophobia, is a widespread problem in western societies. This fear is not only of spiders but can extend to all land arthropods with more than six legs—the arachnids. It can range from simply avoiding arachnids to panic attacks, high heart rates, and flight behavior. It's not clear if arachnophobia is a learned response or something instinctive. However, it is much commoner in western societies than elsewhere. In other parts of the world, spiders may even be part of the diet. Fear of spiders can result in stress, wasted time, and environmental costs through overuse of insecticides. Insecticides are often used to kill spiders, but unless you directly spray the spider or its web, insecticides have little effect.
What are arachnids?
Arachnids include spiders, mites, ticks, scorpions, harvestmen, whip scorpions, camel spiders, and vinegaroons. Of these, only spiders, mites and ticks, and scorpions have venom. Arachnids differ from insects in several ways. They have eight or more legs and two major body parts, the cephalothorax (a fused head and thorax) and abdomen. They don't have wings or antennae. Spiders are different from other arachnids because they can spin silk from structures called spinnerets at the end of the abdomen. They are much more commonly found in homes and gardens. Spiders do not have chewing mouthparts or legs modified to capture prey, so they rely on venom to both incapacitate their prey and begin digestion..
In California, spiders commonly encountered around buildings include jumping spiders, tarantulas, orb weavers, sheet web spiders, cellar spiders, wolf spiders and widow spiders.
Which spiders are dangerous?
Culturally, we're taught to fear certain spiders more than other arachnids, except for scorpions. Among these are black widows, brown recluse, and hobo spiders. Many issues are attributed to spider bites. However, in most cases of “spider bites” spiders were not actually involved. A sharp pain followed by development of a lesion or sore is not a sign of a spider bite but could instead be due to a staph or strep bacterial infection.
Humans are largely unaffected by the venom of most spider species. During the entire 20th century, only about 100 deaths from spider bites occurred worldwide.
Only a few spiders have venom that is dangerous to humans, including the Sydney funnel web spider of Australia, widow spiders (Latrodectus), Brazilian wandering spider, and the African sand spider.
Widow spiders
The only potentially dangerous spiders in California are widow spiders. Both the native western black widow spider and the invasive brown widow spider occur in California. These are smooth bodied, shiny spiders, with long slender legs, and a bulbous abdomen in the females. They appear to be hairless. Females have a bright hourglass shaped mark on the underside of the abdomen.
Widow spiders make messy webs in sheltered sites. The silk is several times as strong as silk produced by other spiders and has a different feel when touched. These tough silk threads are also smooth and homogeneous. During WWII widow silk was used to make the crosshairs in gunsights for the U.S. Army.
Widow spiders are abundant in urban and suburban habitats. In some regions of California there might be as many as 20 to 30 black widows per property. They are shy, reclusive spiders and live in quiet dark places. They generally retreat into hiding places when confronted by any animal larger than they are. Actual widow bites are rare and rarer still do they inject venom. Instead many widow bites are what are called dry bites. Black widow venom is neurotoxic and can cause fever, muscle and joint aches and muscle cramping. It does not cause sores, and it is rarely fatal. There is an effective antivenom available for treating black widow bites.
Recluse spiders
Recluse spiders also have bad reputations. These are ground-dwelling spiders in the genus Loxosceles that somewhat resemble wolf spiders. There are several species across the U.S., but only two occur in California, L. deserta and the introduced L. laeta, but most people focus on the brown recluse, L. reclusa. California has the largest number of diagnosed brown recluse spider bites in the U.S., yet the brown recluse does not occur within 1,000 miles of California. Essentially, all recluse bites in California are probably bacterial infections.
True to their name, recluse spiders are very shy and occur in dark quiet places. Recluse spiders appear to be even more reluctant to bite than widow spiders. In an example of this, in the early 2000's a Kansas family began collecting spiders in their century old farmhouse. After one year they had collected more than 2,000 brown recluse spiders. No one had ever been bitten.
Hobo spiders
Hobo spiders, Eratigena agrestis, are found in Washington and Oregon, and perhaps far northern California. This spider is also a ground dweller and resembles a small wolf spider. Online, its bite is said to be as dangerous as recluse spiders, causing necrotic sores. This is also an urban myth. Sores attributed to hobo spiders are generally caused by bacterial infections.
For more information on spiders, see Dr. Kimsey's webinar on the UC IPM YouTube channel.
[Originally featured in the Fall 2022 issue of UC IPM's Home & Garden Pest Newsletter.]
- Author: Lauren Fordyce
The UC IPM Urban & Community Program hosts monthly webinars that are free and open to the public. Join us every third Thursday from 12pm-1pm for helpful pest related information. All webinars are recorded and posted on the UC IPM YouTube channel soon after.
Upcoming
10/20/22: Trees for a Changing Climate
With fall finally here, now is a great time to plant trees and shrubs. However, before you head to the nursery, consider attending this webinar on Trees for a Changing Climate. On October 20, 2022, UC ANR Environmental Horticulture Advisor Janet Hartin will discuss some underutilized trees that are heat, drought, and pest resistant. Sign up for this webinar here.
11/17/22: Using Disinfectants and Wipes Safely
Since the onset of the pandemic in 2020, many people began using disinfectants more often around the home, in the office, and at school. Like any chemical product, these materials should be used safely. On November 17, 2022, Meredith Cooks from the National Pesticide Information Center will help you understand how to safely use these products in a variety of settings. Register for the webinar here.
Past
9/15/22: Arachnophobia
On September 15, 2022, Dr. Lynn Kimsey led a webinar on arachnophobia and dispelled some common myths about spiders. The recording for that webinar has been added to the UC IPM YouTube channel.
See all of our future and past webinars at https://ucanr.edu/sites/ucipm-community-webinars/.
- Author: Karey Windbiel-Rojas
Are you concerned about pesticides in our waterways? Join us on August 18, 2022 at noon for UC IPM's free monthly webinar to learn how to keep surface water clean by reducing pesticide use and runoff. The webinar will be presented by Karey Windbiel-Rojas, Area Urban IPM Advisor and Associate Director for Urban & Community IPM with the UC Statewide IPM Program. Register today to serve your spot!
Hate spiders? Love them? On September 15, 2022 we'll feature a webinar on Arachnophobia! Dr. Lynn Kimsey, Director of the Bohart Museum of Entomology at UC Davis, will discuss various common myths and misconceptions about spiders. You don't want to miss this one! Register at https://ucanr.zoom.us/webinar/register/WN_CXwGEwWvRAOWw8FUjBOcvg .
As always, both webinars will be recorded and posted on the UC IPM YouTube channel within 3 weeks of the live webinar. No continuing education units (CEUs) will be offered for those with California DPR licenses. UC Master Gardeners and others can request CEU approval from their local program coordinators.
Hope to see you there!