Orb Weaver Spider - Mangora placida
Bugguide.net calls this spider Tuftlegged Orbweaver
Araneae (Spiders) / Araneidae (Orb Weavers) / Mangora / Mangora placida
Live adult spiders photographed in the wild at Warrenville, Illinois. Size: 5-7mm
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Orb Weaver Spider - Mangora placida
Orb-weaving spider

Orb weavers (Family Araneidae) comprise a huge family of spiders, of which there are several hundred species in North America. These spiders vary greatly in color, shape and size, measuring between 2 - 30mm (1/16 -- 1 1/4") long. They have eight eyes arranged in two horizontal rows of four eyes each. The males are generally much smaller than the females and commonly lack the showy coloring of their fairer sex. They often spin their own smaller orb web near an outlying portion of the female's, and I've noticed most males give the females wide berth. Indeed, I rarely see male orb weavers, they are so reclusive.

Most orb weavers spin spiraling webs on support lines that radiate outward from the center; the plane of the web may be vertical or horizontal or somewhere in between. Many of this family replace the entire web daily, spinning a new web in the early evening (this usually takes about an hour) and deconstructing the web each morning in a ritual almost as complex as the spinning process: they gather the silk into a ball and eat it for reprocessing. Our page on the Neoscona orb weaver has a series of pictures showing this process. I find them doing it only in the early morning, usually when the rising sun first illuminates the top of the web.

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Orb Weaver Spider

Orb Weaver Spider

Orb Weaver Spider

Orb Weaver Spider

 

Orb Weaver Spider - Mangora placida
This female spider did not have an orb web, but built an irregular, nearly invisible not-quite-sheet web

Stabilimenta (below) are conspicuous lines or spirals of silk, included by many diurnal spiders at the center of their otherwise cryptic webs. It has been shown spider webs using stabilimenta catch, on average, 34% fewer insects than those without. However, webs with the easily-visible markings are damaged far less frequently by birds flying through the web. It is an evolutionary tradeoff the spider can influence every time it builds a new web. The inclusion of stabilimenta is influenced by many factors, including prey density and web location.  Read the scientific study at Behavioral Ecology magazine.

In any event, stabilimenta or no, an orbweaver spider planted firmly head-down in her web amongst tall weeds and grasses remains maddeningly invisible to man and beast.

Argiope female spider with web stabilimenta
Argiope female spider with web stabilimenta (picture is rotated -90 degrees for clarity).

 

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