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Project Lab 

May 18, 2012

Lions and tigers and SPIDERS! Oh my!


Last week, my imaging work in the Project Lab involved taking pictures of two distinctive California spiders, the aggressive false tarantula (Calisoga longitarsus) and the California turret spider (Atypoides riversi). Both of these species belong to the mygalomorph spiders (fangs work in a parallel position), a group which includes the familiar tarantulas. They are both ground dwelling hunting spiders which do not use webs for prey capture.

The Calisoga spider is found in Central and Northern California oak and coniferous woodlands to about 2300 feet, and is often seen in urban areas, often in swimming pool filters. Spiders live in burrows or crevices that are partially lined with silk, where they wait for passing prey of small to medium arthropods. “I can’t believe it’s not a tarantula!” is the common comment of people who observe this hairy spider, which can be brown to silvery in color. Males are usually easier to find, as they are ‘vagrant’, particularly during mating season. Despite their aggressive behavior, they are not dangerous to humans, though they will bite if harassed. The males have special spines on their lags that act as claspers during mating. Males generally die soon after mating, females can live several years.

Atypoides riversi

The California Turret Spider is another large spider that builds burrows in the ground with silk linings, and a built-up turret of silk and debris that blends into the background when closed. When hunting at night, the spider opens the turret and lies in wait for passing prey, which it senses by vibrations. Males are often observed wandering at night during the rainy and mating season, and can be observed looking for females if one walks around on forested paths at night with a flashlight. As with most other California spiders, their bite is not considered dangerous to humans. Look for the distinctly elongated pedipalps of the male, mouthparts adapted for reproductive purposes.  These spiders can have a considerable life span in the wild (up to 16 years)

Until next time,
Vic Smith


Spiders of North America, D. Ubick et al, American Arachnological Society 2005

The Natural History of the California Turret Spider, L. Vincent, The Journal of Arachnology , 1993

Filed under: Uncategorized — project_lab @ 9:56 am


  1. I am from Washoe Valley Nevada (89704) and just found one in my back yard. Very interesting looking spider. It took a while to find a web site that identified it for me. Took a good picture of it.

    Comment by Justin — October 13, 2012 @ 6:36 pm

  2. I currently have what seems like a Calisoga nest nearby or in our house (Pescadero on the Ca. coast) we’ve found several juvenile males within in a very short period, just last night I spotted 3 out at the same time but in different parts of the house! We assume that they are looking for a mate, it’s the right time of year for it. Luckily we are fairly comfortable with spiders and critters in general, but after my experience last night, I’d really like to learn more about their potential aggressive behavior.

    I always find them at my feet, running toward me or just past me as I step aside. This night, it seemed like all three took calculated moves, waiting for the right moment, hiding and then reappearing and bolting directly toward me, even changing the direction of its path to do so. I’m not sure if they are heat seeking, following the light of my flashlight or if they put out a scent when in danger to notify other spiders, (b/c I was catching multiple spiders at the same time) or if they’re aggression can go so far as to hunt down their human hunter; but in all my years living in the mountains and on farm land, it was a definitely the closest “Arachnophobia” movie moment I’ve ever experienced!

    At the end of my adventure, I closed my bedroom door to go to bed, re-opened my door about 5 minutes later and found the one of the three that had gotten away. It was directly in my doorway, facing in and about to slip under my door. I panicked and closed the door and pushed a towel into the gap. Another 5 minutes later, I checked the door, and could see one segment of a leg coming in between the towel and the door. I was shocked! I guess it could have been coincidence, and maybe it was just trying to find what it could find, but can’t say that for the first time in my life I was genuinely scared that a spider was actually trying to get me.

    I know there must be a logical explanation for this behavior, even if its that my own mind is what perceived the danger, but what I actually observed was unique to any spider experience I’ve ever had before.

    Comment by Rose — October 16, 2012 @ 10:45 am

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