Sunday, December 18, 2011

Spider Sunday: Tinus peregrinus

Nursery web spiders of the family Pisauridae are more diverse than I thought. I had been under the impression that there were only two genera in North America: Pisaurina and Dolomedes. Turns out there is another: Tinus. Thanks to Lynette Schimming at, I found out that what I thought were immature fishing spiders I had observed in Tucson, Arizona and Mission, Texas were actually adults of Tinus peregrinus.

Whereas most adult fishing spiders and nursery web spiders are quite large (body length 10-28 mm), Tinus peregrinus maxes out at around 10 millimeters body length, males a millimeter shorter still.

This species ranges across the southwest U.S. from southern California to the southern tip of Nevada, and east to Texas and Missouri. It also occurs in northern Mexico. The “type locality,” the site where the first known specimen was collected, is listed as Hot Springs, Arkansas, but it is suspected that this is in error.

Virtually nothing is known of the life history and biology of this animal. Egg sacs in preserved collections are dated late July and early August. I have observed this species under bark on trees near the edges of ponds, and also at the edges of window frames. It would appear that once an individual spider finds a location that suits it, the spider stays put. One specimen I found in the corner of a window had several shed exoskeletons in its web, suggesting it had resided there for some time. No wonder, the web was also full of tiny midges (flies in the family Chironomidae) that had swarmed the lighted building at night.

Like most spiders in the Pisauridae, T. peregrinus appears to prefer the vertical plane, rarely found on the ground.

Sources: Carico, James E. 1976. “The Spider Genus Tinus (Pisauridae),” Psyche 83: 63-78
Kaston, B. J. 1978. How to Know the Spiders (Third Edition). Dubuque, Iowa: Wm. C. Brown Company Publishers. 272 pp.


  1. I'm near Tucson and will keep my eyes open for this one. I enjoy your blog...sorry for not commenting more often. :)

  2. Looks like I've got quite a few of these hanging about my pond in Phoenix, AZ.

  3. Found around our pool in Goodyear, AZ every summer.

  4. Found around our pool in Goodyear, AZ every summer.

  5. Are these spiders any danger? As my kids found about ten in our filter, I am surprised our pool guy did not take care of this, a family living in the intake of the filter. They started to swim all over the pool after being discovered, upsetting for the kids

    1. No, these spiders are not dangerous. The only truly dangerous spiders that pose any potential risk to the average, healthy human are widows (Latrodectus sp.) and recluse spiders (Loxosceles sp.), and danger from recluse spiders is greatly exaggerated.

  6. We have discovered one of these spiders living in the underside of the opening to our pool skimmer! Pretty good size, too!


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