Why This Venomous Spider is Expanding Into the Northern U.S.

News that a venomous spider is expanding its territory can be concerning. No one wants to be a victim of a potentially life-threatening spider bite. However, in nearly every state in the US, there is at least one species of spider whose bites can cause more than a slight bump and itch.

One of the most abundant venomous spiders across the nation is the brown recluse. While the spider takes the blame for bites it did not cause, there are plenty of unsuspecting people who have been bitten by these spiders. While most of those bitten receive treatment and live to tell the tale, there are a few every year who do not. This is why there is so much fear surrounding brown recluse spiders, and that fear is only likely to grow, founded or not, as the spiders begin to expand northward.

Why Brown Recluse Spiders Are Expanding Northward

Brown recluse spiders are currently found in southern and midwestern states, where the climate is hospitable for them not only in terms of their prey but also habitat and temperature. However, due to climate change, the parts of the US that the spiders have called home are forecasted to disappear.

According to Erin Saupe, a researcher at the University of Kansas, ecological computer models have been able to predict the brown recluse spider’s range in 2050 and 2080.

“The actual amount of suitable habitat of the brown recluse doesn’t change dramatically in the future time slices,” Saupe explains, “but what is changing is where that area is located.”

The projections show that just 5% of the area brown recluses currently inhabit will be habitable by 2080. This means that the brown recluse population will significantly decrease if there are no significant changes to combat climate change.

If this comes to fruition, the only states that would be habitable to brown recluse in the future include:

• Wisconsin

• Michigan

• Indiana

• Ohio

• Pennsylvania

• New York

• Nebraska

• South Dakota

In addition to climate change taking away territory that has historically been home to brown recluse spiders, the creatures they hunt as prey may begin to die off as well. This includes crickets, which are not highly adaptable to prolonged days of severely high temperatures. This means the brown recluse will face a climate that is too warm to live in and a lack of resources to survive.

Some Species Would Thrive If Brown Recluse Spiders Go Extinct

To some, the disappearance of the brown recluse population may seem like a great idea. After all, this would mean fewer of these spiders to contend with. However, there is one pest that would grow out of control quickly: the cockroach. This is because the warmer the temperatures, the more active cockroaches are. They will be more frequently seen and multiply faster as the warmer it is, the more apt cockroaches are to mate.

It should not be surprising that this species would thrive given how long and how many different climate changes cockroaches have lived through. Consequently, without brown recluse spiders to keep the cockroaches and other pests in check, there may be bigger problems than fearing being bitten by a brown recluse.

Brown Recluse Spiders Will Need Help Migrating

Brown recluse spiders are homebodies, which means they do not venture far from where they have built their homes. Being a recluse species (hence their name) is problematic in terms of migration, something that will need to be done if the brown recluse wants to survive.

According to Catherine Scott, PhD, a Postdoctoral Fellow at McGill University, brown recluse spiders are “poor dispersers” and move very little for “weeks to months at a time.”

“In a study, the maximum distance any individual traveled in a single day was about 10 meters, but the vast majority did not move at all or moved less than 1 meter per day,” Scott explains. “Many of these spiders will stay in the same location for weeks or months at a time.”

Consequently, according to Scott, brown recluse spiders are unlikely to move to habitats that are better suited for them as temperatures rise on their own. They will need help to do so.

“The primary way that they end up in new habitats outside of their natural range is being moved by humans,” Scott says. “They like to live in crevices in things like cardboard boxes and are often found in places where people store things for long periods (basements, garages, attics), so when people move, they can inadvertently bring brown recluse spiders with them.”

Scott concludes, “When they are transported to new locations, recluse spiders will typically remain in the building where they were introduced (remaining for years without spreading to new areas).”

As these spiders make their way to new territories that have never dealt with brown recluses, methods for handling native pests are not effective and, according to Scott, can cause more harm than good in some instances.

Insecticides Are “Ineffective and Harmful”

Many do not know that pest companies not well-versed in ridding homes of brown recluse spiders can actually cause more harm than good. According to Scott, standard insecticides used to remove pests from homes are ineffective in killing brown recluses. “Reputable pest control companies that have experience with brown recluses can help to eliminate them from buildings,” Scott explains. “This can be challenging in places outside the native range of brown recluses, where pest controllers don’t typically encounter this species.”

Scott continues, “It’s important to know that controlling spiders requires different methods than most insects, and attempting control using insecticides can be ineffective and even harmful.” Therefore, if one of these spiders has managed to hitchhike into an area it is not native to, seeking expert advice will be necessary, as regular pest control methods will only introduce poison into the environment and not remove the problem.

What To Do If You Come Across A Brown Recluse Spider

Given that brown recluse spiders are among the most dangerous arachnids, it is important for those who live in areas where they are common to know what to do if they encounter one.

If the brown recluse spider is outside, experts recommend leaving it alone and containing it if it can be done safely. From there, contacting a pest control company to determine if there is just the lone spider or more to contend with will help homeowners understand what they are dealing with.

Brown recluse spiders found in nature, away from homes, and minding their own business should be left alone.

For those who believe they have a brown recluse in the home, be it because they saw it or they have seen the web, removing all of the areas the brown recluse would want to live is necessary.

To create an environment that is inhospitable for brown recluse spiders, the following should be done:

• Secluded areas should be closely inspected

• Seal cracks to keep the brown recluse spiders from getting into the house

• Vacuum constantly to prevent spiders from setting up their home

If bitten by a brown recluse spider, these steps should be immediately taken:

• Clean the bite with soap and water

• Cover the area with a wet, cold cloth or apply ice to reduce swelling

• Keep the area elevated where the bite occurred, if possible

• Seek medical attention as soon as possible to alleviate pain and other common symptoms

• For symptoms that become severe (ex., rash, fever, dizziness, chills, or vomiting), seek medical attention immediately

As scary as the thought of brown recluse spiders may be, given their potent venom, it is important to remember that the spiders do play an important role when it comes to insect and other pest control. Therefore, unless they are in a spot where there is the potential for being bitten, the spiders should just be left alone. Remember, they do not actively look to bite people. Biting primarily occurs when the spiders feel threatened or provoked.

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