Misconception Monday – Comic: A Spider Did Not Bite You

This comic, A Spider Did Not Bite You from Buzz Hoot Roar, is just plain fabulous.

https://i1.wp.com/buzzhootroar.com/wp-content/uploads/BeatriceSpidersLARGE-01_biggest.jpg

All credit goes to: Roar and Katie McKissick. AKA Beatrice the Biologist, McKissick is a blog and science comic that hopes to make science fun and interesting for the casual reader. Visit www.beatricebiologist.com to see more of her work, and follower her on Facebook and Twitter.

Misconception Monday: Brown Recluse are Everywhere!

As a spider scholar (of sorts), I tend to get a lot of questions from just about everyone regarding the more infamous spider species. One of these species, the brown recluse, is well-known for having venom that is somewhat poisonous to humans, and so it has become somewhat of a curiosity to most individuals in the United States. Typically, people want to know how deadly this species is, where this species likes to live (i.e. inside or outside), and how to ID an individual spider as a brown recluse. Although there’s quite a bit of misinformation regarding these questions, the question I want to answer today is “What is the geographic range of the brown recluse (Loxoceles reclusa)?”

The main reason this question interests me is that, throughout North America, there is an intense, widespread fear of the brown recluse. Yet, if you look at the actual geographic distribution of spiders in the Loxoceles genus (see the map below), it is clear that the brown recluse species really only lives in a small part of the United States.

Loxoceles map courtesy of: http://spiders.ucr.edu/myth.html
Loxoceles map courtesy of UCR Spider Myths

Still, ignorance of the geographic range of this spider has two ramifications: 1) many spiders being misidentified and killed due to fear that they may be Loxoceles, and 2) people paying substantial amounts of money to have exterminators get rid of harmless spiders (this could be due to active scamming by exterminators, but I would guess that, more often than not, exterminators may not know how to identify brown recluse any better than their customers).

So, please use this map as your first means of identifying whether or not a spider in your house/work/garden/etc. is a recluse or not. If you do live in an area with recluse, or are just curious about this fascinating genus, please read more about them at the sites listed below. There is quite a bit of false information about the brown recluse on the internet, so it’s best to stick to websites and articles that are clearly written by people that research these critters!

http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7468.html

http://spiders.ucr.edu/brs.html

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1071166/

http://www.burkemuseum.org/spidermyth/myths/fiddleback.html

Misconception Monday: Is spider silk stronger than steel?

In keeping with the theme of these next few weeks (spider silk), today’s post will address a common idea: that spider silk is stronger than steel. In researching the topic of spider silk, I kept coming across this “fact” in articles across the web, with a number of writers quoting that “spider” silk was specifically five times stronger than steel or tougher than Kevlar, or a myriad of other weird claims. Although I certainly believe that some spider silks could be stronger than steel, what concerned me initially about this statement is that it seems too simple to always be true. To begin with, I found it hard to believe that any scientist(s) had experimentally tested the tensile strength of silk of all 40,000+ species of spider. In addition, spider silk varies quite a bit in composition, so to think that all spider silk was exactly (or even approximately) 5x stronger than steel seems unlikely, even if spider silk in general is stronger than steel. Therefore, I set out on a mission to find where this statement might have originated…. and sort of came up empty.

That is, while there have been many studies of the basic physical properties of spider silk (here’s one example: Griffiths&Salanitri1980), fewer than 100 species have actually had their silk tested. Why the idea that spider silk is 5x stronger than steel is so widespread, I’m not exactly sure. My guess is that someone must have calculated this once, for one species, and one specific steel alloy, and then it somehow caught on because it sounds interesting and is easy to remember.

In conclusion, this MM topic is going under the category of true for some species, with an additional note that the phrase “spider silk is stronger than steel” is misleading and needs further testing. Why? Because spiders are highly variable, within and across species, and to claim that every spider in the world produces silk that is stronger than steel would simply be unfounded. However, direct measurements of spider silk have shown that some spider silk can have a tensile strength that is higher than that of certain steel alloys. While this may not be as cool of a fact to state at a party (because I’m sure everyone talks about spider silk at parties…), you would not be misinforming your friends!

Misconception Monday – All spiders and insects belong outside the home.

I think that most people have one of two basic reactions whenever they come across a spider (or any other arthropod/bug) in their home. There is…

1) “ACKK that thing is sooo gross ewww UGH smush it/get it out of here/flush it down the toilet!!!”

or there is…

2) “Aww poor lil’ guy, why are you inside? Let’s put you back outside where you belong!”

While the tone is a bit different in each of these reactions, the message is the same: many humans believe that bugs don’t belong inside the home. Yet, we find them in our homes all the time, and we spend a lot of time/money trying to eradicate them. So, then, is it true that spiders don’t belong “inside,” and if not, why do we feel this way?

The answer to the first part of the posed question is simply, no. As much as we humans like to separate ourselves from all other animals and from nature in general, we are a huge part of the natural world. And, as part of the natural world, many animals have evolved to coexist with us and our cosmopolitan ways, spiders included. Though there surely can be species that roam into homes randomly from time to time, there are a number of spiders that live in/on man-made structures for their entire lives. For example, the Common House Spider (Parasteatoda tepidariorum) prefers to build webs on or in buildings (if you live in the U.S., you have probably seen them in barns, sheds, attics, etc.). Moving these spiders and other house spiders to bushes or trees outside would not help them survive, and would be an unnatural habitat for many spiders found in the home.

Answering the second part of the posed question is a bit simpler: we don’t like seeing spiders in our homes because we think that they are pests. However, spiders are more like pest control, than pests, themselves. Many house spiders eat insects like mosquitoes, fruit flies, ants, and cockroaches – essentially, all the bugs that we really don’t want in our homes.

So, if you can, try to accept the spiders that you see hanging out in your house, because they’re more likely helping you than harming. However, if you really can’t stand the sight of them, and you absolutely have to move them somewhere else, try to move them into a shed, or attic/closet you don’t access much, instead of outside.

LiveScience – “The suprising cause of most ‘spider bites'”

Just ran across this great article that explains how many “bites” that people self-diagnose as spider bites, are unlikely to actually be caused by spiders. It may seem that I stress this misconception a lot on the site, but it is one of the main reasons why people are so scared of spiders, and so willing to harm them or to look at them in disgust, when really, they are such fascinating creatures! Spider bites do occur, and can be dangerous, but the reality is that they are quite rare compared to much *more* dangerous arthropods and diseases.

OK. Enough ranting from me… Enjoy your week, and if you find any cool spiders, feel free to send me some pictures or stories about them!

Misconception Monday – Do all spider bites leave two fang marks?

Many people think that the characteristic mark of a spider bite is two symmetrical marks in the middle of a bite. Sort of like this (Note: do not search for “spider bite” under Google Images if you are easily grossed out):

Spider bite or not?

Well, I’m here to set the record straight. Yes, spiders do have fangs at the tips of their chelicera that they use to bite and inject venom into their prey (See: How Stuff Works – Spider Venom). Therefore, it is possible that if a human received a spider bite, there would be these distinctive fang marks. However, the reality is that spiders rarely bite humans at all, and if one did bite, most spiders are likely too small to ever leave two fang marks that are clearly visible to the human eye. In addition, two side-by-side marks are not always indicative of a spider bite. Many arthropods can bite more than once, leaving marks that might look like two fang marks to us, but really are two separate bites. Because of this, spiders can certainly be wrongly-accused of biting humans much more than they actually do (on the other hand, if the spider is small enough, it could get away with it!)

The easiest way to tell if a bite is from a spider or not is to catch the perpetrator in the act. Unfortunately, once you notice a bite, it is usually too late. If you are really worried that you’ve been bitten by one of the few dangerous spiders out there, then there will be other symptoms to look for. The number of bites that you see may hint at whether it is a spider bite or not, but is not a form of diagnosis, alone.