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.

Sheetweb weaver, Drapetisca alteranda

I was fortunate enough to find many interesting insects and spiders while living in South Deerfield, Massachusetts in 2009. One nice surprise was stumbling upon a specimen of the sheetweb weaver Drapetisca alteranda. Not only is this spider quite small (females are only 4-4.5 millimeters in body length), but it is exceedingly well camouflaged. Oh, and nocturnal, too.

This spider is atypical of the family Linyphiidae and can be easily mistaken for something like a lynx spider or other hunting spider that does not spin a web, but waits in ambush instead. Drapetisca lives on tree trunks where it sits motionless. Close inspection reveals that it is actually not in contact with the surface of the tree, but sprawling across the thinnest of snares.

It was by sheer luck that I noticed the specimen imaged above. I was seeking insects and arachnids around a bright light outside the town library the night of July 30. The light illuminated not only the exterior of the library, but a nearby tree as well. Ants, beetles, and other insects paraded up and down the trunk, and I found at least one Common House Spider in her snare under a branch. My flashlight eventually revealed the Drapetisca at roughly shoulder height, much to my surprise and delight.

Male specimen, © Tom Murray via Bugguide.net

This spider is, unfortunately, best identified by characters that are not easily observed in the field. The jaws are armed with a set of three or four long spines that criss-cross (see image below). The female’s external genitalia (epigynum) are also diagnostic, but that necessitates turning the spider over and putting her under a microscope. Still, the overall appearance of the spider, and its posture on its web, help to eliminate other potential suspects.

© Charley Eiseman, "Bug Tracks" blog

As is the case with most organisms that are of no economic importance, precious little is known of this spider’s biology and distribution. It appears limited in its range to southern Canada and the extreme northern U.S. It is common in New England, and recorded from the Great Lakes region, Montana, Alberta, and British Columbia. It may be absent from the northern plains.

Female with egg sac, © Kyron Basu via Bugguide.net

Your own persistence and patience in seeking spiders like this one could reveal much new information. Nothing ventured, nothing gained, so do share your own images and observations.

Sources: Eiseman, Charley. 2011. “Kleptoparasite,” Bug Tracks blog.
Hollenbeck, Jeff. 2006. “Species Drapetisca alteranda,” Bugguide.net
Kaston, B.J. 1978. How to Know the Spiders (3rd Ed.). Dubuque, Iowa: Wm. C. Brown Company Publishers. 272 pp.

Spider Sunday: Hammock Spiders

What could be more relaxing on a Sunday afternoon than lounging in a gently-swaying hammock in the backyard? Well, don’t ask any of the hammock spiders in the genus Pityohyphantes. Their “hammock” is not for relaxing but for capturing insect prey.

Hammock spiders are in the sheetweb weaver family Linyphiidae, and their webs are more often slightly convex rather than concave. The silken platform is suspended by a maze of threads above it, it just doesn’t sag very often. There are sixteen species in North America, mostly occurring in the coniferous forests of the west and north. Shown here are two specimens from western Massachusetts, and one from the Front Range in Colorado. The very name Pityohyphantes is Greek for “pine weaver.” Look for their webs in hardwoods, too, usually in foliage and well off the ground.

I was surprised to find the Colorado specimen shown below hanging in the middle of its web, upside down beneath the sheet. Usually, these spiders conceal themselves on the underside of foliage on the periphery of the snare. They may also construct their webs on fences or the exterior of buildings and other manmade structures.

The spiders themselves are not particularly large. Mature females are around 5-7 millimeters in body length, the males slightly smaller. Mating takes place in the spring, at least in the species Pityohyphantes costatus. The female attaches her egg sac to a twig or other object on the edge of the web. Apparently both adults and immature specimens may pass the winter under bark, or stones on the ground.

Hammock spiders are fairly easily recognized by the consistent pattern on the abdomen, a brown or reddish jagged-edged band down the middle of the back, on an ivory background. Reliable identification of the species can only be accomplished by examining the external genitalia.

How do you tell hammock spiders (or any sheetweb weaver for that matter) from cobweb weavers? One clue is the legs. Cobweb weavers have legs free of spines, whereas sheetweb weavers generally have prominent setae on the legs. Obviously, the webs can be a clue as well, though some cobweb weavers like Steatoda do spin a sheet-like web with a maze of tangled lines above and below their webs.

I have not found hammock spiders to be nearly as abundant as other sheetweb weavers like the Bowl and Doily Spider or various dome spiders, but I haven’t been looking intensely for them, either. See if you can find them around your own neighborhood or local park. Of course, you’ll have to get out of your own hammock to do that….

Sources: Kaston, B. J. 1978. How to Know the Spiders (Third Edition). Dubuque, Iowa: Wm. C. Brown Company Publishers. 272 pp.
Moulder, Bennett. 1992. A Guide to the Common Spiders of Illinois. Springfield, Illinois: Illinois State Museum Popular Science Series, Vol. X. 125 pp.
Weber, Larry. 2003. Spiders of the North Woods. Duluth, Minnesota: Kollath+Stensaas Publishing. 205 pp.