Spiders: Fascinating Arachnids of Illinois

Spiders often evoke fear, ranking among common phobias like snakes, heights, and public speaking. However, this negative perception is largely undeserved. While almost all spiders possess venom-injecting fangs, most of the 3,500+ species in the United States can’t pierce human skin. Serious bites are rare, comparable to mosquito bites or bee stings, and spiders are generally not aggressive.

Why are Spiders Feared?

The fear of spiders, or arachnophobia, doesn’t affect everyone. If spider bites were truly dangerous, wouldn’t this fear be universal? Another theory suggests spiders are simply “creepy.” Their eight legs, ambush tactics, and silk webs contribute to this perception.

The Wonders of Spider Silk

Spider silk, a marvel of nature, is five times stronger than steel yet 30 times thinner than human hair. Spiders use this silk for various purposes:

• Webs: Trapping prey
• Retreats: Sheltering from danger
• Prey Subduing: Immobilizing captured insects
• Nests and Nurseries: Protecting eggs and young
• Movement: “Draglines” for descending and “ballooning” for long-distance travel on wind currents

Identifying Spiders: Beyond the Basics

Beyond the eight legs and fangs, spiders possess unique characteristics:

• Eyes: Most have eight, with size and arrangement as key identifiers.
• Pedipalps: Sensory appendages near the fangs, used by males for courtship and mating.
• Body Structure: Two-part body (cephalothorax and abdomen), classifying them as arachnids, related to mites, ticks, and scorpions.

Spiders Found Outdoors in Illinois

Illinois boasts over 500 spider species, with a few frequently found indoors or around structures.

Crab Spiders (Thomisidae)

These spiders are named for their crab-like movement and leg arrangement. Instead of webs, they ambush prey on flowers and vegetation, often camouflaged to match their surroundings. Bites are rare and insignificant.

Orb Weaver Spiders (Araneidae)

Orb weavers are the spiders of Halloween decorations, known for their large, intricate webs.

They are typically found outdoors, often in tall vegetation or attached to structures. Garden spiders, with their striking black and yellow markings, are a common example. While their bites resemble bee stings, they are uncommon.

Jumping Spiders (Salticidae)

Jumping spiders, with their fuzzy appearance and large, front-facing eyes, are considered “cute” by some.

They are active hunters during the day, pouncing on prey. Their bites, though sharp, are not dangerous.

Woodlouse Spider (Dysdera crocata)

This spider is sometimes confused with the brown recluse due to its six eyes and nocturnal habits. They are identified by their reddish legs, dark reddish-brown front, and gray abdomen. Bites, though potentially painful, are not serious.

Nursery Web Spiders (Pisauridae)

These large spiders resemble wolf spiders and are known for the female’s habit of creating a silk “nursery” for her eggs and young. Fishing spiders, a type of nursery web spider, are found near water and can even walk on the surface. Bites from nursery web spiders, while painful, are not dangerous.

Wolf Spiders (Lycosidae)

Wolf spiders are large, hairy spiders that are active hunters. They are identified by their two larger eyes. Females carry their egg sacs and spiderlings with them. Bites, while noticeable, are not dangerous.

Funnel Web Spiders (Agelenidae)

These spiders create distinctive funnel-shaped webs and are known for their speed.

Common examples include grass spiders and house spiders. While some species, like the hobo spider, have been associated with necrotic wounds, this is not well-documented, and they are not considered dangerous in the United States.

Spiders Found Indoors

Some spiders are commonly found indoors, including:

• Cellar Spiders (Pholcidae): Known for their long legs and sheet-like webs.

• Cobweb Spiders (Theridiidae): Identified by their bulbous abdomens and irregular webs. Black widow spiders belong to this group but are not typically found in homes.

• Sac Spiders (Miturgidae and Clubionidae): Create small, tubular webs (“sacs”) and are active hunters at night.

Brown Spiders (Sicariidae)

The brown recluse spider, found primarily in the southeastern United States, is a cause for concern. Identified by its brown color, violin-shaped marking, and six eyes (instead of eight), this spider is reclusive and bites are rare.

Managing Spiders

Effective spider control involves a combination of methods:

• Exclusion: Sealing cracks and gaps in structures to prevent entry.
• Habitat Modification: Reducing vegetation and clutter around homes.
• Web Removal: Regularly destroying webs.
• Sticky Traps: Trapping spiders that wander in search of prey.
• Pesticides: Used as a last resort and applied by a professional.

By understanding spider behavior and utilizing integrated pest management strategies, spider encounters can be minimized.