Sunday, February 22, 2015

Bridge Orbweaver (Gray Cross Spider)

Downtown Portland, Oregon features a promenade on both sides of the Willamette River, and it is a stroll, bike ride, or jog worth taking simply for the scenery and people-watching. Should you be interested in spiders, it is even more worthwhile. Many manmade structures are occupied on the exterior by the Bridge Orbweaver, Larinioides sericatus. Even in December and early January of this year, specimens of varying ages were abundant.

This species is also known as the "Gray Cross Spider," and it is easily confused with the very similar Larinoides patagiatus, which has no common name. Further complicating matters, the Bridge Orbweaver has been going by the Latin name L. sclopetarius until very recently. A revision of the genus Larinioides was published in the journal Zootaxa about two months ago (see citation below).

These are fairly large spiders, mature females measuring 8-14 millimeters in body length, and males 6-8 millimeters. Their legspan makes them appear even larger to the untrained eye. Both genders share the same distinctive pattern on the carapace (top of cephalothorax) and abdomen. The overall color is generally gray, but some specimens tend toward brown.

Mature male from Massachusetts

The spider normally hides in a retreat on the periphery of its circular web during the day, and emerges to repair or reconstruct the snare at night. The spider then spends the night in the hub of the web, hanging head down. The spiders can also be there in the center of the web on overcast days, and juvenile specimens tend to be more likely to occupy the hub during the day than mature individuals.

Female making a kill in Massachusetts

While this species is particularly common close to water, where emerging aquatic insects like midges and mayflies are an abundant food source, I have also seen the Bridge Orbweaver in other settings in western Massachusetts. It can be a fixture around outdoor lights, where insect prey is drawn in great numbers. Spiders are quick to take advantage of resources like that, and competition for prime "web sites" is keen.

Underside of adult female, Oregon

Larinioides sericatus is found not only in the U.S. and Canada, but Europe as well. It is strongly suspected that it was even introduced to North America from the Old World. Records from Asia are now attributed to yet another species, L. jalimovi. Here, the Bridge Orbweaver is known from the maritime provinces, Quebec, Ontario, Alberta, and British Columbia south to Minnesota, Wisconsin, Illinois, Indiana, Ohio, New England, Virginia, Kentucky, Washington, and northwest Oregon. Isolated records exist for extreme northeast North Carolina, Oklahoma, and northwest Utah, at least some of which probably need confirmation. Recent voucher specimens have been taken in Long Beach, California.

Special thanks to Ivan Magalhäes and Laura Lee Paxson on the Facebook page for the American Arachnological Society for setting me straight as to the proper scientific name for this species.

Sources: Bradley, Richard A. 2013. Common Spiders of North America. Berkeley: University of California Press. 271 pp.
Dondale, C. D., Redner, J. H., Paquin, P. & Levi, H. W. (2003). The insects and arachnids of Canada. Part 23. The orb-weaving spiders of Canada and Alaska (Araneae: Uloboridae, Tetragnathidae, Araneidae, Theridiosomatidae). NRC Research Press, Ottawa, 371 pp.
Hollenbeck, Jeff, et al. 2013. "Species Larinioides sclopetarius - Gray Cross Spider,"
Šestáková, Anna, Yuri M. Marusik, and Mikhail M. Omelko. 2014. "A revision of the Holarctic genus Larinioides Caporiacco, 1934 (Araneae: Araneidae)," Zootaxa 3894(1): 061-082.


  1. Great blog, Eric! I just IDed my first one at home recently and this makes for excellent reading to get up to speed on its natural history:

  2. Hello
    I have been trying to figure out what kind of spider I found last year. I got some really good puctures. I live in Ottawa Canada. Is there a way I can send you the picture and get you expert opinion?
    Deb Vachon

  3. Awesome blog, I've been observing these spiders for the past 8 months and a lot of what I observed is in here plus more! Thanks Eric

  4. I would like to know if the spider in my backyard is a Gray Cross spider or a wolf spider, and if either one is poisonous. How do I send the photo?

    1. For security reasons I do not accept photos on this website. Best to upload to a secure photo-sharing site and then provide a link....or tag me on a Facebook post or something.

  5. I know I am very late to comment but I just woke up to a huge round web that is primarily on my siding and drain spout but crosses over to an iron bench on the other side of my porch. I'm in North Central Maryland. I used an app to identify but the pics are spot on!

    1. There is never a deadline for commenting here. Glad this post was of help to you! Thank you for sharing your observation.

  6. Eric, seven years after your post - I'm writing on bridge spiders for my nature column in Maine, and have run across the L.sericatus name a couple of times now. So you're aware: in the World Spider Catalog, L. sclopetarius is still the accepted name, and L. sericatus is given as a synonym - "Larinioides sericatus (Clerck, 1757) | Araneidae synonym = Larinioides sclopetarius"


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