Illinois Natural History Survey - University of Illinois

 

Illinois Spiders

Carolyn Nixon

 

More than 500 species of spiders live in Illinois.  While all spiders have venom,  most spiders are harmless to humans because their fangs are too small to puncture the skin.  Most alleged cases of spider bites are likely insect bites or other small injuries that have become infected by bacteria.  Spiders are generally not aggressive towards humans and are actually beneficial predators.  They are fascinating creatures to observe, especially once you learn to recognize the different types.  Learn to recognize the two dangerous types and then enjoy the rest.

 

Here are some of the more commonly encountered groups of spiders.  When you find a spider, try to determine which group it belongs to.

 

Web building spiders (spider webs are often easiest to view in early morning, when they are covered with dew).

black__yellow_argiope_dorsal_view.jpgorb_web.jpg• Orb weavers—these spiders spin very intricately designed webs attached to plants and structures.  The webs are usually vertical, with strands of silk radiating out from the center and sticky cross-strands circling the center.

 

 

 

 

 

 

 

 

 

Sheetweb_Spider_PN.jpg

Sheetweb_PN.jpg

• Sheet web—these spiders spin small, sheetlike platform webs in plants, such as grass and branches of trees and shrubs.  They often go unnoticed until they are covered with dew.

 

 

 

 

 

Funnelweb_spider_closeup.jpgFunnelWeb_PN.jpg• Funnel web—these spiders spin sheetlike webs with a funnel-like tunnel at one end.

 

 

 

 

 

cobweb_spider.jpg• Cobweb spider—these spiders spin a loose tangle of silk, often most noticeable inside structures such as houses. 

 






Spiders without webs

Wolf_spider_PN.jpgCrabSpider.jpg• Wolf spider (left)—these often large, somewhat hairy spiders roam the ground and low foliage as they hunt for prey.  Some species are quite large.  They can be easily seen at night with a head-lamp.  (See "The Naturalist’s Apprentice, Shining for Spiders," INHS Reports, Autumn, 2007)

 

• Crab spider (right)—these crab-shaped spiders sit and wait to ambush prey.  They are often camouflaged, matching the color of a flower or leaf.  They are often only noticed once the observer sees the prey insect dangling from its fangs.

 

 

 

jumping_spider.jpgFishing_spider.jpg Jumping spider (left)—these stocky, short legged, quick moving, hairy spiders are recognizable by their jerky movements.  They hunt down their prey and jump onto it.  They often have interesting markings and have large, forward-looking eyes.

 

• Fishing spider (right)—these spiders closely resemble wolf spiders, but are found near, and often on water surfaces.  They can dive underwater where they catch small fish or tadpoles.

 



Venomous spiders

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• Brown recluses—Loxosceles reclusa (left) make loose, messy webs, but are often seen away from the web.  These are brown spiders with long, thin legs.  There are no spots or stripes on the abdomen or legs.  Their legs have no spines and are never dark brown.  They have a light-colored cephalothorax (the head area) with a distinct, dark brown violin-shaped marking. They are neither hairy nor shiny. 

 

• Black widow (right)—is an orb weaver that is glossy black with a red, hourglass-shaped marking on the underside of the abdomen.  Many similar looking spiders have red markings on the top of their abdomens.  These are NOT black widows.  Two species of black widow occur in Illinois (Latrodectus mactans—southern black widow, and L. various—northern black widow).  The northern black widow is seldom found around human habitation, but the southern black widow was once common in outhouses, where people were often bitten.

 

Handy references

A Guide to the Common Spiders of Illinois. Bennet Moulder. 1992. Illinois State Museum Popular Science Series, Vol. X.

A Golden Guide to Spiders and Their Kin. Herbert W. Levi and Lorna R. Levi. 1968. Golden Press.

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