Unraveling the web of brown recluse myths in Florida

Story and mulimedia by Joey Garcia, University Communications and Marketing

Chills run down many people's spines at the mere thought of a spider, sometimes causing panic or even disgust. However, according to USF alum Louis Coticchio, spiders, especially the brown recluse, shouldn't be portrayed as villains. His newly published findings aim to change the narrative by debunking common myths of this misunderstood arachnid.

"This research shows that brown recluse spiders aren't the boogeyman that everyone makes them out to be," Coticchio said. "They aren't swarming throughout Florida, infiltrating homes and attacking. Rather, they are misunderstood and want to be left alone while rarely showing signs of aggression, even when provoked."

MAKINGS OF THE SPIDER-MAN

Long before Coticchio became an expert in spiders, he was a child with a curiosity for the outdoors.

"Growing up in Largo, I was catching and keeping everything I could find while playing outside," Coticchio said. "I would bring in rattlesnakes, alligators, you name it. Though they would frighten my mother, it sparked my early interest in biology."

He would continue that passion into his undergraduate career as a biology student on the USF St. Petersburg campus. Coticchio focused on the brown recluse starting in 2019 when he joined Associate Professor Deby Cassill's lab. He also launched the Florida Brown Recluse Spider Project to further educate and conduct research on the topic.

"Lou is the gift of a century, and every research professor needs one brilliant student like him," Cassill said. "He walked into my office as a freshman as a self-guided person with a great work ethic and a passion for changing how we think about spiders. I felt very fortunate to play a part in this research led by him; he's the real Spider-Man."

INSIDE LOOK AT THE BROWN RECLUSE

Coticchio's research focused on three key questions, beginning with whether brown recluse spiders are widespread across Florida. The species is not native to the state and is primarily found in parts of the Midwest and Gulf coast. To assess their presence locally, Coticchio investigated 220 properties that reported suspected infestations.

Findings confirmed breeding populations of the invasive Mediterranean recluse at only 19 sites, with populations ranging from one to 171 spiders per location. These sites were concentrated mainly in central and north Florida.

Coticchio's attention then turned to studying their aggression. In controlled testing, he gently provoked brown recluse spiders by applying light pressure with gel-based tools. He then recorded how often they bit. Wolf spiders were used as a comparison, biting about 80% of the time when provoked, while recluse spiders mostly only bit when severely stressed, such as when squeezed or held upside down.

The study also examined one of the most feared outcomes of a bite: necrosis, or tissue death. Coticchio found that when bites occur, they typically produce shallow wounds about half a centimeter deep. In rare cases, necrosis can develop, but it is usually limited to the skin's surface layers and does not extend into muscle or bone. Most verified bites result only in redness, burning or small blisters that heal over time. Severe wounds often attributed to recluse spiders are more likely caused by bacterial infections, such as staph.

CHANGING THE NARRATIVE

Coticchio's published findings lay a foundation for educating both the public and the scientific community. The study has already gained widespread attention, including coverage by the popular Facebook and YouTube group All Bugs Go to Kevin, which shared the research with an audience of more than 300,000 viewers. Coticchio now looks forward to presenting his work to additional local and medical audiences.

Coticchio also plans to continue investigating a mystery population of Mediterranean recluse spiders discovered in St. Augustine. He hopes to determine whether the group originated from a single introduction event or multiple arrivals over time, which could reveal how its population might grow.

"The research community has been very open to our study," Coticchio said. "We sensed there was an urgency to get this study out there and prove the narrative toward the brown recluse has been overblown. I'm not saying that they're completely harmless, but rather they're reluctant to bite, and there's an extremely low percentage of encountering them in Florida."