Marbled Orb Weaver Spider - Araneus marmoreus
Orb Weaver Spiders - Family Araneidae
Insects & Spiders | Spiders Index | Jumping Spiders | Wolf Spiders
Live male and female spiders photographed at northern Illinois Size = Female 15mm. Male = 8mm
Marbled Orb Weaver Spider - Araneus marmoreus
Spider is still active in mid-October. She had captured dozens of winged queen ants from a nearby swarm (below).
Orb weavers comprise a huge family of spiders, with 3500 species worldwide, 180 of which call North America home. 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. Orb weaver males are generally much smaller than the females and commonly lack the showy coloring of their fairer sex.

Orb weavers show the greatest range of sizes and appearance than any other family of spiders. Their presence on human's structures and their conspicuous web probably account for their less-than-welcome status among people otherwise uninterested in such matters. Orb weavers are completely harmless to human and their pets, but still inspire fear in most people.

I know I could never tolerate one of these touching me, but I find them fascinating and beautiful creatures. Murderous, indeed, but nature is red in tooth and claw, after all. There is much I admire in their industry, adaptability, persistence and above all, efficiency as predators.

Female Marbled Orb Weaver with scale = 15mm
Female measures 14.5 mm. She built a web on the wall of my garage and hid underneath the wooden trim.
Orb weaving spiders often add stabilimenta to their webs. Stabilimenta 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.
Marbled Orb Weaver Spider with Queen Ants Prey
Along with a flower beetle, this happy female captured dozens of queen ants from a nearby ant swarm

Male Marbled Orb Weaver Spider
Male Marbled Orbweaver

References
  1. Bugguide.net "Araneidae"
  2. Wikipedia, "Orb-weaver spider"
  3. The Kouroo Contexture, "People mentioned in (Henry David Thoreau's) 'The Maine Woods' "
  4. Archives, Gray Herbarium Library, Harvard University Herbaria, "Harris, Thaddeus William 1795-1856
Class Arachnida / Order Araneae: Spiders are the largest group of arachnids.  They are easily recognized by their eight legs, and there are few creatures great or small that elicit such irrational fear in mankind. The vast majority of spiders are completely harmless and offer beneficial services, chief of which is keeping the burgeoning insect population in check.  Spiders Index | House Spiders | Jumping Spiders
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