Cobweb Spider - Steatoda triangulosa
Family Theridiidae - Cobweb Spiders
, Scaffold Web Spiders, Comb-footed Spiders
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Live female spiders and egg cases photographed indoors at Dupage County, Illinois.
Cobweb Spider - Steatoda triangulosa
Cobweb spiders' webs are disorganized, unlike the circular webs made by orb-weavers and other web-building spiders. Cobweb spiders have 8 eyes and 8 legs, 2 body parts, and fang-like mouthparts called chelicerae. Most cobweb spiders live for less than 1 year. At the end of the summer, female cobweb spiders produce a large amount of eggs that they wrap in an egg sac made of silk.

Cobweb spiders undergo simple metamorphosis: all spiders' young hatch from eggs and look like tiny adults. They shed their skin as they grow. Common in North America, these little gals can be found almost anywhere there are weeds, fences, trees, walls, or other upright structures on which to build their webs. Cobweb spiders are predators, and they will eat almost anything that is small enough to get trapped in their webs.
House spider egg cases and hatchlings
Cobweb spider egg cases and hatchlings. Parasteatoda tepidariorum
Like most web-building spiders, cobweb spiders tend to have poor vision - they don't need to see very well because they can "feel" prey when it gets caught in their webs. Most cobweb spiders are considered beneficial to humans. They eat flies, mosquitoes, flies, and other spiders.
Cobweb Spider - Steatoda triangulosa
I can tolerate these gals living in the garage but not the house!
References
  1. Bugguide.net, Steatoda triangulosa
  2. Arthur V. Evans, National Wildlife Federation Field Guide to Insects and Spiders & Related Species of North America (Sterling, 2007).
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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. I am continually amazed at the resourcefulness of these supremely successful predators.
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