Sunday, May 29, 2022

Spider Sunday: Scarlet Sheetweb Weaver

Exploring our modest property the other day I had the good fortune of encountering a small but striking spider on the exterior of our garage. It was a male Florinda coccinea, known as the Scarlet Sheetweb Weaver or Black-tailed Red Sheetweaver. At only 3-3.5 millimeters in body length, it is usually difficult to spot despite its bright red color, with black accents.

The males are generally more conspicuous than the females if only because they must travel to find one or more mates. They are shockingly agile for a species that is normally most at home in a silken snare. They appear acutely aware of motion, at least a large creature like myself, and I almost missed out on getting an image at all, as the spider dropped suddenly into foliage below.

Last fall, on October 8, 2021, my wife and I were on a morning neighborhood walk. A large group of bright orange mushrooms growing in a strip of lawn in a park caught our attention, which in turn led us to spot several small, dew-covered sheet webs in the grass. It is no wonder these spiders are so difficult to find. The silk of their webs is so fine that the sheets are nearly invisible unless coated in water droplets. We found both males and females in the webs, which makes me think this species may have more than one generation each year.

Curiously, most scientific references consider Florinda coccinea to be a mostly southeastern species, though it ranges north to at least Maryland and southern New Jersey, and west to Missouri and the eastern edge of Kansas. It might be expanding its range northward and westward, or simply be so inconspicuous to avoid detection by the few people out there seeking spiders. We collectively have much to learn about the actual geographic distributions of most arachnid species.

Florinda coccinea, a member of the family Linyphiidae, is identified by the black tubercle on the rear of the abdomen, a feature not seen in similarly-colored spiders. I also learned that they are exceptionally adept at feigning death when they perceive a threat. I was convinced my poor male was deceased or nearly so, but offered it a little water with the tip of an artist's paintbrush, and left the spider and the brush in a casserole dish overnight. The next morning the spider was much more lively, and after a quick photo session it was released outdoors.

Sources: Howell, W. Mike and Ronald L. Jenkins. 2004. Spiders of the Eastern United States: A Photographic Guide. Boston: Pearson Education. 363 pp.
Marshall, Sam, and G.B. Edwards. 2002.Florida's Fabulous Spiders. Tampa: World Publications. 65 pp.
Gaddy, L.L. 2009. Spiders of the Carolinas. Duluth, Minnesota: Kollath+Stensaas Publishing. 208 pp.
Kaston, B.J. 1972. How to Know the Spiders (Third Edition). Dubuque, Iowa: Wm. C. Brown Company Publishers. 272 pp.
Bradley, Richard A. 2013. Common Spiders of North America. Berkeley: University of California Press. 271 pp.

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