Common Spiders that Invade Iowa Homes: Bites, Prevention & Identification

Spider Species Commonly Found in Iowa Homes

Over 500 species of spiders live in Iowa, but only a handful are regularly encountered inside homes across the state. Most Iowa house spiders pose no threat to people, but some bites can cause mild reactions. Learn how to identify common house-dwelling spiders in the area to safely deal with eight-legged roommates.

Cellar Spiders

Long-bodied cellar spiders frequently inhabit dark corners of Iowa basements and crawl spaces. Named for their tendency to build messy, chaotic webs in storage areas, cellar spiders have a light brown color with striped or banded legs spanning around half an inch long. They prey on other household pests like flies or moths trapped in webs. Cellar spider bites very rarely break skin and only cause slight irritation in extremely rare cases of sensitivity.

American House Spiders

American house spiders rank among the most common spider species found inside Iowa homes year-round. Ranging between quarter and half dollar sized, these light tan to dark brown spiders set sheet webs in undisturbed corners of garages, window wells, or crawl spaces. Despite urban myths, house spider bites cannot penetrate human skin and are harmless beyond causing temporary redness.

Southern House Spiders

Southern house spiders share a habitat with American house spiders under rocks or woodpiles in Iowa yards and homes. Adults reach just over a half inch with grayish-yellow bodies and long front legs. They build small, loose webs hunting down prey. Uncommon bites produce only mild swelling, although venom can very rarely trigger serious reactions in sensitive individuals. Seek medical treatment for severe swelling or ulceration.

Grass Spiders

Funnel weaver grass spiders spin dense webs across Iowa lawns that funnel insects towards fangs and venom used to immobilize prey. Adults measure roughly one inch with a brown cephalothorax and grayish abdomen with black and white stripes. Grass spiders venture indoors in fall seeking mates, but generally avoid contact with humans. Fatally venomous to insects, grass spider bites very rarely break skin and principally cause only temporary pain when they do.

Fishing Spiders

Iowa’s largest spider species, fishing spiders hunt along water edges rather than building webs to trap food. Adults reach over two inches with hairy brown bodies and light bands on legs. Despite intimidating size, fishing spider bites occur infrequently indoors in fall months as males wander while mating. Bites swell slightly and cause mild pain subsiding within a few hours, posing little medical risk for most people.

Jumping Spiders

With excellent eyesight, jumping spiders actively stalk and pounce on prey instead of spinning silk webs waiting for food to become ensnared. Found on plants both outdoors and inside Iowa homes, jumping spiders measure around half an inch with stocky, fuzzy bodies colored black, brown or gray. Non-aggressive jumpers prefer to flee from humans, but may deliver dry, harmless test bites seemingly out of curiosity. Pain usually disappears within 5-10 minutes.

Sac Spiders

Beige to pale yellow sac spiders frequent Iowa homes hiding in silken retreats folded into crevices or holes indoors. Less than a half inch long, the spiders emerge at night to wander walls and ceilings hunting for meals. Although sac spider bites rarely break skin, venom can produce burning pain, redness and swelling lasting a few days for sensitive individuals. See a doctor if bitten.

Preventing and Controlling House Spiders

While most house-dwelling spiders in Iowa pose minimal safety risk, no one wants to feel outnumbered by scurrying arachnids. Reduce chances of infestations using integrated pest management techniques that humanely prevent access and limit resources inviting spiders inside.

Seal Possible Entry Points

Install weatherstripping around doors and caulk cracks in home foundations and openings for pipes or wires to close gaps over 1/16 inch that allow spiders to sneak indoors seeking food, moisture and shelter. Properly fitted screens also obstruct spider migration while permitting ventilation.

Reduce Clutter

Cardboard boxes, woodpiles, debris and other clutter offer prime hiding spots for spiders invading Iowa homes. Properly storing items in sealed plastic totes helps eliminate appealing harborage. Regular cleaning and organizing ensures fewer dark spaces exist where spider webs can escape notice and expand unchecked.

Keep Landscaping Trimmed Back

Shrubs, trees and foliage touching an Iowa home’s exterior provide handy bridges allowing spiders on plants access to interior nooks through walls or gaps in siding. Prune vegetation back at least 2 feet from the house and keep mulch beds pulled back slightly from foundations to hinder spiders from traversing inside via landscaping.

Fix Lighting Issues

Outdoor security lights or other illumination shining on the house can attract nighttime flying insects, drawing the attention of outdoor spiders hoping to feed. Switch bulbs to sodium vapor lights less appealing to bugs or redirect lighting shining directly on the home at night to diminish a spider buffet right outside Iowa residences.

Employ Natural Spider Repellents

Spiders tend to avoid strong smells given their sensitivity to scents. Herbs like mint, garlic, lavender or basil sprinkled around likely spider entry points or applied along baseboards emit odors repugnant to spiders. Concentrated eucalyptus, tea tree, citrus or peppermint oils also deter spiders when applied judiciously around garages and crawlspaces.

Vacuum Regularly

Use a hose attachment to vacuum up egg sacks, webs and spiders themselves residing in undisturbed corners once a week inside an Iowa home. Pay special attention to basements, cellars, garages and attics where spiders congregate. Ensure the vacuum cleaner completely seals canisters or bags after use so no spiders escape back into the house.

Identifying and Treating Venomous Spider Bites

Iowa only hosts two types of dangerously venomous spiders requiring extra vigilance - northern black widows and northern brown recluses inhabiting sheds, woodpiles and other infrequently disturbed spots statewide.

Black Widow Bites

Northern black widows build messy webs outdoors and under debris only venturing occasionally into Iowa homes unintentionally trapped in objects moved inside. Females measure just over a half inch long with red spots on a shiny black body and legs. Unique red hourglass marking sits on the bottom abdomen segment.

Tissue damage results from potent neurotoxins in black widow bites causing painful muscle cramping at the wound site progressing to rigid abdominal muscles. Seek medical assistance immediately if bitten to receive antibodies combatting venom spread.

Brown Recluse Bites

Ranging from half inch to one inch long, violin-shaped brown recluses exhibit sandy brown bodies with slightly darker violin shapes behind their heads.Six equal-sized eyes arrange in pairs with legs lacking conspicuous markings. Recluses actively avoid people when possible but bite readily if unexpectedly disturbed or trapped against human skin.

Recluse bites usually appear minor initially before pain spreads outward redness develops. Within 24-36 hours, necrotic lesions seep clear or bloody drainage marking dying underlying tissue. Antibiotics fight infection as venom destroys collagen, needing months to fully heal while leaving significant scarring.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.