Saturday, July 31, 2010

Arachnophobes, Stop reading Now!

Rambo in the shower- click to enlarge
This is the story of Rambo, our resident Wolf Spider.  A healthy four inch leg span means that he generally shows up before we step on him.  He spent several days in the shower recently, close enough to the outlet handle that we had to reach down slowly to avoid scaring him.
As Joel Vance says in the Missouri Conservationist article Spider! Spider!,
"I also like wolf spiders, gray and ominous. They are predators, stalking and killing other insects, and I like to believe that some of the insects they kill are ones I don't want around, maybe even brown recluses."
When I started the article, we kept Rambo around to hold down brown recluse.  It turns out that there is no evidence to support this.
 
Brown Recluse- click to enlarge
Some sources mention that a small wolf spider can resemble a brown recluse.  A brown recluse is generally less that 3/4 of an inch.  One site suggests that you can tell the difference by the fact that the brown recluse has only 6 eyes.  While true, if you can count the eyes on a spider that small, you are way too close!   Even finding the "fiddle" on the top of the cephalothorax is a challenge if the spider is alive and not in a container.
Missouri Wolf Spider**
If you ever look into Rambo's eyes with a magnifier you can see that he is a soulful spider.  There are 8 eyes, as in the picture, and the upper two large ones showing how sensitive he is.  The two brown hairy structures below are the chelicerae, used for grasping its victims.  These are hollow in spiders and eject venom through the black fangs visible on the inner tips.   
I use the term "he" advisably, as Rambo could be Rambette.  I have never been able to see the palps clearly.  Larger club palps are a male feature, necessary to transfer sperm into the specialized female opening.
Speaking of Rambette, there is interesting research which shows that a female wolf spider (Schizocosa uetzi) can recall information three weeks later.  The males have distinctive patterns on different individuals legs which they wave around to entice females.  Researchers painted different colors on the legs of males and exposed immature females to different color-legged males.  Three weeks later when the females reached ssexual maturity, they selected males of the specific color they had seen three weeks before.  and they tended to eat males of the with the other color legs rather than mate with them. * And you thought your teenage years were dangerous.
Unfortunately there isn't any direct evidence that wolf spiders eat brown recluse but since Rambo spends a lot of time in our bathroom and closets, I am sure that he runs into them frequently.  On the other hand, recent research from the University of Kansas shows that brown recluse spiders prefer dead stuff over killing their own dinner.  Zoogoer*
"New research by Jamel Sandidge, a biologist at the University of Kansas at Lawrence, shows that brown recluse spiders scavenge rather than hunt if given a choice. It's the first time a spider has been shown to prefer scavenging over predation.
Brown recluse spider
There can be as many as 2,000 brown recluse spiders in one house.
Sandidge didn't set out to study the hunting and eating habits of brown recluses—his study was focused on the relative population densities in houses of brown recluses, other spiders, and insects. As the study progressed, however, Sandidge made several unexpected observations about brown recluse behavior. In houses, he saw them eating insects that had obviously been dead for a long time. He also saw them running away from insects. He has even watched a brown recluse remain motionless while a potential prey insect walked over it. In the lab, Sandidge says, "I was feeding them yellow mealworm larvae and the problem was that the mealworms were eating the spiders." Sandidge began killing the worms before putting them in the enclosures with the spiders, and the spiders readily ate them.
Sandidge's curiosity was piqued. He set up new experiments, offering the spiders dead prey and live prey. More than 80 percent of the time, the spiders chose the dead prey. 'Brown recluses are very fragile and very weak,' Sandidge says. They often lose legs or even their lives in encounters with live insects, which may explain why they prefer to avoid them."  from the Smithsonian Zoogoer

If you search"brown recluse" in Google you will get lots of fear mongering sites created by exterminators.  If you see an ad, move on.  Brown recluse bites occur rarely and many "spider bites" are something else.  There is good information at the Wikipedia page or here.
Even if they don't actively eat brown recluse, wolf spiders hunt lots of other insects we don't want in our house.  Rambo (or Rambette for Ann) has a secure future in our creek house.

* These stories and a lot more interesting spider facts are at this highly recommended Smithsonian Zoogoer site.  For instance, did you know that:
  • One species of Black and Yellow Garden Spider (Argiope aurantia) dies spontaneously as soon as he inserts his second palp in a female to deliver his sperm, even if he does it mistakenly.  
  • A type of jumping spider called Portia is able to learn about its spider prey's preferences.  It plays "music" by setting up vibrations in its spider prey's web.  Trying different "tunes" until it gets a response, it then learns that tune and stays with it until the prey comes toward it.  Portia is also able to strategize, even taking an hour or two to sneak around a tree or object to approach its prey from the back side.  That is a lot of memory time for a spider, (or even an older Master Naturalist.)
** Picture by Dan Johnson
Editors Note:  Sadly, we must report the demise of Rambo, or a wolf spider that looks like him, found dead Monday night in the downstairs bathroom.  There were no signs of trauma (i.e. boot marks or compression injury) and we assume that he died in the line of duty, keeping the shower safe from crickets, beetles and possibly brown recluse.  Thanks for the memories.


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