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Spiders are getting meaner in the Southeast — because of hurricanes, study finds

Floating colonies of fire ants and homeless copperheads are often associated with hurricanes in southeastern United States, but scientists have found another, less expected consequence: Nastier spiders.

“Compelling evidence” uncovered by a team from McMaster University reveals aggressive spiders are the most likely to thrive after a tropical storm, suggesting coastal storm-prone areas are seeing an unpredictable insect evolution.

And it’s only going to worsen, they predict.

“Cyclones consistently selected for more aggressive spider societies. Furthermore, sites where cyclones have historically been more common also harbor more aggressive groups,” according to the report published in BioRXiv.org.

Did Carolinas really have millions of floating fire ants during Hurricane Florence?

“As the environmental impacts of cyclones only promise to grow as sea levels rise, the pressure to understand the environmental impacts of these storms has never been more pressing,” the report says.

The researchers reached their conclusion by studying 240 spider colonies before and after the impacts of Tropical Storm Alberto, Hurricane Florence and Hurricane Michael, all in 2018, according to the report.

The three storms had a combined death toll of around 100 people in the U.S., and caused millions of dollars in damage. The subsequent flooding also scattered venomous snakes, fire ants, and even alligators into populated areas in search of dry ground.

Included among the test sites were spider colonies (Anelosimus studiosus) in both Carolinas, Georgia, Alabama, Mississippi and Florida, the report states. The tests included “vibrating” spider webs to see how many attackers responded within two minutes (a test of “colony aggressiveness”).

What they found was an “evolution of colony behavior” that was more aggressive in those areas impacted by tropical storms, the report concludes.

Why the more aggressive colonies thrived is a mystery that needs more study, the researchers say.

However, one explanation is that hurricanes may limit the amount of prey to be shared among spiders, making aggressive “attack” spiders more apt to procreate, they say.

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