- 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
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.
- 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
- Author: Anne E Schellman
In Part I, we discussed why mosquitoes bite, and which mosquito species can spread West Nile and Zika virus. Now, let's talk about what mosquitoes need to reproduce, how to prevent them from breeding around your home, and best methods to protect yourself and your family while outdoors.
What do Mosquitoes Need to Breed?
The mosquitoes that spread West Nile virus and Zika need water to lay their eggs. Female mosquitoes can lay their eggs in even the smallest amount of water. Places in your yard that appeal to them include standing water found in ponds, garden pots, children's toys, or even pet water bowls. Eliminating these possible breeding spaces is key to mosquito control.
Watch the video “Don't Let Mosquitoes Breed in your Yard” from UC IPM for helpful tips.
Protect Yourself from Mosquito Bites
There's a plethora of mosquito control and prevention items for sale, but many are ineffective.
When outdoors, protect your skin by wearing long-sleeved pants and shirts, long socks, and a hat. Be aware that mosquitoes can bite through a thin layer of clothing. Also, choose and apply an effective EPA-registered mosquito repellent that contains DEET, picardin, IR3535, or oil of lemon eucalyptus to exposed skin.
You may be tempted to use outdoor sprays to battle mosquitoes. However, this method is only temporary and doesn't help control the source of the problem. The best way to avoid bites are prevention and protection.
Resources: UC IPM Pests in the Urban Landscape. Zika, Mosquitoes, and Repellents. https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=21923
- Author: Rick Vetter
[Reblog from Pests in the Urban Landscape]
If you were to ask an audience of more than a few people if they or anyone they know has ever seen or been bitten by a brown recluse spider in California, many hands would be raised. This is quite remarkable because the brown recluse spider has NEVER established breeding populations in California!
The myth of the brown recluse has been generated and sustained by:
- Physician misdiagnoses (where many skin lesions of diverse non-spider origin are blamed on a non-existent spider)
- Media articles that report claims of horrendous bite injury without proof of spider involvement
- Misidentification of harmless brown spiders as brown recluses by the general public as well as "authorities" who lack adequate spider identification skills
Brown recluse mythology is persistent throughout North America, even in places such as Alaska and Canada, which are far from where the spider is actually found. In some places, it is easy to argue against this myth because no recluse spiders have ever been found there. For California, this argument is less definitive because the state's south eastern deserts are home to several related native species such as the desert recluse spider (a different species than the brown recluse).
Additionally, in urban Los Angeles County, there have been rare records of isolated populations of the Chilean recluse spider. However, the native desert species occur where few people live and the Chilean recluse has only been found in commercial buildings, never in homes. There have been no confirmed bites by this non-native Chilean recluse since it was originally found in Los Angeles in the late 1930s. There have been rare findings of brown recluse in California, but these have occurred as hitchhikers in moving boxes from other areas of the country and the spider was destroyed after locating.
Although there are some recluse spiders in limited areas within California, this does not explain the hundreds (and maybe thousands) of brown recluse bite misdiagnoses made in California each year. In a study mapping out such misdiagnoses vs. known populations of recluse spiders in California, more than 95% of the purported brown recluse bites occurred in urban areas where the spiders are not known to inhabit.
For many decades throughout North America, it has been readily assumed by the medical community that many skin lesions resulted from brown recluse spider envenomation. However, recent research shows that most of these lesions are unrelated to spiders. Causes include some medical conditions that are much worse than any recluse bite would be.
One real danger of such a recluse bite misdiagnosis is that the actual causal condition will not respond to recluse bite remedy, allowing the real condition to continue on unabated, worsening and potentially leading to death. Some of these afflictions misdiagnosed as recluse bite include: cancer, leukemia, lymphoma, Lyme disease, bacterial infections, anthrax, adverse reaction to blood thinners, poison ivy, poison oak, chemical burn, thermal burn, and more. One of the most common conditions misdiagnosed as a spider bite is the bacterial infections caused by methicillin-resistant Staphylococcus aureus (MRSA).
To find out more about the different species of recluse spiders, identifying features of the brown recluse, and other spiders commonly mistaken for recluses, see the recently updated Pest Notes: Brown Recluse and Other Recluse Spiders on the UC IPM website.