Unscheduled House Guests
Spider Trivia

Introduction by Carol Rawle

Within a few days of each other, both Bill Wenstrom and Mary Schwyzer had a large, dark, scary looking spider visit them.  They both asked me if I knew what it could be.  Mary's was even more intimidating because it literally had hundreds of baby spiders hithhiking on it.  When I proved to be a dry source of info, Bill Wenstrom decided to research this awesome arachnid himself.  What he found is both interesting and entertaining.

Research by Bill Wenstrom

There's little doubt that our spiders are both members of a common group of spiders called "Wolf spiders".  The scientific family name is Lycosidae.  The generic name may be Lycosa, although several other genera are possible.  The species name is unknown since I can't find a good key to genera much less species.

In any case, Wolf spiders are common and of global distribution.  About 1,500-2,000 species are known.  Perhaps more than 100 species occur north of Mexico.  Interestingly, they typically make up a high proportion of the spider population in very cold climates and at higher elevations.  I have more specific info on yours (obviously an adult female) than mine (probably an adult male) but if I find anything of further interest, I'll let you know.

They are described as medium to large, fast-running, hairy spiders, actually related to Tarantulas.  They are diurnal (operate both during daytime and nitetime).  So their eyesight is very well developed as opposed to nocturnal species that rely more on other senses.  Lycosas are actually burrowers.  They dig and hide in a burrow in the ground and then dart out to ambush a food item when it passes by.  Other genera are simply hunters that hide under leaves when they're not wandering about.  I've seen some small burrows out near my shed which I intend to inspect to see if spiders are living in them.

There are several important characteristics of your spider that aid in identification.  One is the pattern and placement of its eyes.  (See the photo below which shows eyes almost identical in size and placement.)  Your spider has three rows of eyes: two small eyes placed on the top of the cephalothorax (the front portion of its body), two large eyes on the front, and a row of four small eyes below the two large eyes.  The top eyes allow it to see behind and to the sides.  The large eyes are to quickly home in on prey, and the four small eyes are for close-up examination of what it catches.

A second characteristic is that the posterior pair of the four pair of legs is the longest and typically held stretched out behind the spider as yours did before I froze it.  The legs also have hair-like spikes or spines sticking out from them, also an identifying characteristic of Wolf spiders.

The third characteristic is that females surround their eggs with a sac of webbing and carry it around with them attached to "spinnerets" which are little organs on the posterior end of the abdomen (the back end of its body) actually used by other spiders to spin webs (see photo above).  Wolf spiders don't spin webs.  They hunt on the ground by predation on other insects.  They are reportedly of value in agricultural areas since they control crop pests.  They are also non-poisonous and reportedly harmless to people (although certain persons may react more adversely than others to bites) .  One article even identified them as "nice pets" that must be provided with water in captivity.

In any case, I found traces of the egg sack clinging to your spider's legs.  The eggs, therefore, probably hatched fairly recently.  After the eggs hatch, the spiderlings (in your case at least 113) climb aboard the mother who carries them around as they further develop (see photo below).  This is another identifying characteristic.

In addition to the above, males have the habit of more widely ranging as fall approaches in search of a female with whom to mate.  Because of their excellent eyesight, the males actually do a little courtship dance by waving the large, hairy pedipalps (shown in the eye photo as the leg-like appendages to either side of the spider's "beard") in the air as they approach a female.  Both genders apparently try to move into houses as the weather cools in search of prey that become less available outdoors.  Hence, they're found in sinks (like mine) and around windows and doors (like yours).

Unless you want yours back, I'll hold on to her.  Perhaps I'll find some more in burrows.  In any case, I'll probably send them along to the Denver Museum of Science and Nature sometime.  As I mentioned, they have an on-going Spider Survey for CO and accept specimens from anyone who wants to submit same.  I checked their website and didn't find any listings from Las Animas County, just clusters of observations around Boulder and elsewhere where there are colleges.

Hope that you find this interesting.  Cheers-