As autumn leaves begin to turn and the temperature begins to drop, people aren’t the only ones looking to get cozy indoors, as many Iowans notice an increase in insect and spider populations around the home during fall. While finding unexpected spiders hiding around the home can be alarming for some, Zach Schumm, insect diagnostician with the Plant and Insect Diagnostic Clinic at Iowa State University, explains that most spiders in Iowa pose little threat to people.
Typically, spiders or other insects that enter indoors are looking for warmth, according to Schumm. While any spider has the potential to accidentally work its way indoors, the types of spiders commonly encountered in the home include wolf spiders, funnel weaving spiders, jumping spiders and cellar spiders.
“The common offenders are the spiders that are more noticeable, either because they are larger or we happen to see them when they aren’t hiding,” explained Schumm.
“In the United States as a whole, there are very few medically significant spiders that people need to be concerned about. The typical offenders we hear about, the brown recluse and the black widow, are very uncommon in Iowa,” said Schumm. “In addition to being very uncommon, these spiders are typically nonaggressive toward people. Even when they do bite, they often dry bite, meaning that they bite without injecting any venom.”
Brown recluses, the other main species of venomous spider that can be found in Iowa, are also incredibly uncommon. Although their range technically extends into the lower part of the state, they are considered uncommon to extremely rare in the upper Midwest. True to their name, they tend to avoid areas with human activity and rarely bite. They can be distinguished by the dark, violin-shaped marking on their front body section. While bites are not typically immediately painful, a localized burning sensation typically develops within a few hours, followed by raised or darkened skin surrounding the bite. For more information on venomous spiders in Iowa, visit the ISU Extension and Outreach publication “Potentially Dangerous Spiders.”
Since few Iowa spiders pose any real medical threat and are unaggressive, Schumm rarely recommends spraying insecticides around the home.
Zach Schumm continues, “If you want to reduce their numbers, it’s important to seal up any small gaps where they may be entering the home. Putting on new door thresholds, repairing window screens and sealing up cracks can prevent spiders from coming indoors.”
While discovering an unwelcome, eight-legged roommate can be startling, it is rarely a cause for alarm.
“People generally tend to be fearful of spiders, but the spiders we see around our homes aren’t out to get us,” added Schumm. “Next time you find a spider around the house, take the time to observe it for a bit. The more we understand things, the less fearful we tend to be.”