Photo of the Week – May 5, 2017

During the last week, I’ve been lucky enough to find and photograph two different wolf spiders, so I figured I should probably dedicate a short blog post to them.  The first wolf spider I found was a cute little bugger out in the prairie the other day.  I was out looking for monarch eggs and caterpillars and saw the spider scurry between clumps of vegetation.  Since I had my camera in hand, I stopped and had a visit.  The second spider was in our basement and was considerably bigger (2 inches in diameter with legs).  I took it outside where it could be happier, and photographed it before letting it roam freely in our garden.

This big beautiful wolf spider was in our basement before I put it back outside.

There are a lot of big fuzzy spiders that resemble wolf spiders, but true wolf spiders have a characteristic eye pattern that sets them apart.  If you look at the above photo, you can see that there are two large eyes above a straight row of four smaller eyes.  If you look even closer, you might be able to see two additional eyes behind the big ones that point up and to the sides.  You can see those last two eyes more clearly in the photo below.  The layout of those eight eyes is unique to wolf spiders, so if you ever wonder if a big fuzzy spider is a wolf spider, just look it in the eyes and you’ll know.

In this photo, it’s easier to see the wolf spider’s non-forward facing eyes.

There are more than 2,000 species of wolf spiders across the world, and they are a fascinating group of creatures.  Although they are free-roaming spiders (they don’t create a web and hang out on it), they still use ambush as their primary means of hunting.  They’ll usually sit quietly and wait for prospective prey to come within striking range. Wolf spiders hunt mostly at night, and their eyes are well-adapted for seeing in low light.  However, wolf spiders are also very adept at sensing and using vibrations to identify their prey.  Their hairy legs aren’t just for looks; they also act as part of a complex system of vibration sensors.  Wolf spiders can distinguish between patterns of wing beats or footsteps to help them determine what kind of creature is coming near.

This small wolf spider was out in the prairie while I was looking for monarch caterpillars.  Its body and legs were about a half inch in diameter.  Note the distinctive eye pattern that characterizes it as a wolf spider and the different kinds of hairs on the legs.

My daughter made me proud the other day by telling me she was able to impress her college friends with some of my favorite spider trivia: the reason spider legs always curl up when they die.  Spiders have flexor muscles on their legs (muscles that pull the legs toward their bodies) but not extensor muscles to push them back out again.  Instead, they use hydraulic pressure to extend their legs.  A fluid called hemolymph is pushed into the legs, counteracting the flexor muscle pressure enough to extend the legs.  It sounds like a cumbersome system, but if you’ve ever seen spiders run and jump, it’s clear that it works very well.  When a spider dies, it no longer has hydraulic pressure in its legs to counteract the flexor muscles so the legs naturally curl up toward the body.

Don’t you just love spiders?  Of course you do.

Here’s the big female one more time, just before she turned away to go explore our garden.