To Kill or Not to Kill Spiders

I read an article in a small newspaper (Coast News  in Encinitas) about spiders and wrote the author thanking her. It quoted her children’s favorite book, Charlotte’s Web, which happens to be my favorite childhood book, and left me a permanent fondness for spiders and pigs.  None in the author’s family would kill spiders and they were in mourning over the death of a big spider that lived on their front porch.

We too do not kill spiders, none outside our house, and inside we transport any outside (my husband’s exception is black widow spiders).  One of our grown sons confided in me that he, too, cannot kill spiders – you never know in what ways you affect your children.

Orb spiders are one of 2 groups of spiders (or arachnids) the other are hunting or wandering spiders. Each summer my husband and I go out at night with flashlights for orb spider patrols: We watch them get bigger, we witness them taking nights off when they’ve had a particular good haul. And then their webs get messier and messier before they finally disappear (hopefully mating & leaving their egg sack before dying).

Correcting Spider Misinformation

Spiders have an undeserved reputation, with much misinformation, especially about spider bites:

Physicians diagnose swellings as spider bites when they’re really bacterial infections — BUT the prescribed antibiotics will cure the bacterial infection. This reinforces the myth that spiders bite more often than they actually do.  -Rick Vetter, PhD

Do Spiders Bite?

One researcher’s talk I attended said the bites you occasionally wake up with are not spider bites. But other people have witnessed spiders biting them and running away.

From University of California-Riverside entomologist, Rick Vetter (http://spiders.ucr.edu) who has published considerable research on spider bites:

• Spiders do bite but not nearly as often as people attribute them.  Most verified bites by spiders leave a little red mark, a little swelling, and a little itching and then it all goes away by itself.
• Spider bite is a common default diagnosis or what Vetter called a “garbage can diagnosis” – if you don’t know what it is, it MUST be a spider bite….Physicians will diagnose swellings as spider bites when they’re really bacterial infections — BUT the prescribed antibiotics will cure the bacterial infection. This reinforces the myth that spiders bite more often than they actually do.

Vetter says his physician colleagues tell him “that “spider bite” is a nice safe diagnosis because 90% of everything heals by itself — so 90% of the time, physicians look like miracle workers.”  Or the prescribed antibiotics help what is really a MRSA or bacterial infections — this then reinforces to the medical community that antibiotics cure spider bites.

“ The biggest problem is calling something a spider bite (even by doctors) and then having it be something that is very dangerous like group A Strep, cancer, lymphoma, or Staph which can actually kill you. “

BUT… don’t all spiders have venom?

From a University of Minnesota website:

Yes, all spiders have venom but most are harmless to people. (Exceptions are brown recluse, black widows and hobo spiders, although long-term consequences are rare– more info below.)  Few spiders bite, even when coaxed, but if they do, usually when disturbed, most are not painful.

So what’s good about them – why not kill them?

• Spiders are beneficial because of the large number of insects they prey on, including a number of pest species. Properties located in areas favorable to spiders, such as by rivers, lakes, or fields, will have large numbers of spiders.
• Active only at night, they’re shy and usually remain hidden in undisturbed areas, and try to escape when disturbed.
• It’s difficult to eradicate all spiders from a home. It is also unnecessary. Because of their beneficial nature, they are very important to the environment. Tolerate spiders whenever possible. When tolerance is not possible, use an integrated approach using nonchemical methods supplemented with chemical means to reduce spider numbers.

Resources I’ve found useful:

• Common Spiders In and Around Homes
• University of California – Riverside: Spider Research
• U of Washington Spider Myths WebSite

Summaries of Vetter’s Research

Bites of Brown Recluse Spiders (New England Jl of Medicine, 2005 review article)

• • Summary:  In rare instances, bites from brown recluse spiders can cause clinically important dermal necrosis and subsequent scarring. Because of the tendency for medical reports to highlight noteworthy extreme cases … the bite of a brown recluse spider is typically self-limited and self-healing, without long-term consequences.

Recluse Spiders (Loxosceles) Review: biological, medical and psychological aspects (see pdf)

• • Summary: Loxosceles spiders present a venomous  threat for many regions of the world from a shy, reclusive spider. However, the exaggeration of this threat has given this genus a reputation that greatly extends past its actual physical presence.

Myths based in science and medicine (CAB Review article)

• • Summary: Myths are a ubiquitous and persistent part of human culture, which provide comfort and a sense of understanding in a mysterious world. The basis for myths, however, is not always rooted in factual knowledge and they also exist in science and medicine. By employing the mechanisms of the scientific process, a particular myth can be torn down; however, there is a massive amount of inertia given the psychological condition of being human, which is an obstacle to replace myths with facts.