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WHO IS KILLING BLACK WIDOW SPIDER? An unlikely foe
Matthew Cimitile and Joe Rominiecki In a nondescript research lab on campus, Louis Coticchio began placing different species of spiders together in artificial habitats. Red house and triangulate cobweb spiders. Brown widow and black widow spiders. He was interested to see how they would interact. More specifically, he wanted to know if brown widows were playing a part in the dramatic population decline of their more famous black relatives. Originally from Florida, Coticchio spent years as a zookeeper specializing in venomous animals in California. When he returned to the state to earn a biology degree at USF St. Petersburg, he started to collect wild spiders in Florida for a research project. In doing so, Coticchio noticed what other researchers have documented in recent decades: black widow spiders were becoming harder to find. In areas once populated with black widows, the non-native brown widows were becoming increasingly more abundant. “I had a sneaking suspicion that Florida in particular provided plenty of food and habitat for both the brown and black widow to thrive. So, there might be another
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reason such as behavioral differences that was playing a role in this outcome,” Coticchio said. His experiments using artificial habitats sought to answer the cause of this displacement. What he uncovered would lead to international headlines. A misunderstood spider With the exception of Antarctica, widow spiders are found throughout the globe. “Widow spiders typically build permanent homes in structures like garages, sheds, fences and the overhang of houses, so they are a highly visible spider species,” said Deby Cassill, a USF associate professor in the department of Integrative Biology who was Coticchio’s research advisor. “They also have dramatic coloration, with this black shiny body and bright red hourglass. They look like jewelry hanging there. So, for us there is an artistic attraction and, of course, a fear factor.”
Tradition has it that widow spiders received their name via reports of females killing and eating their mate. Though according to the University of Florida’s Institute of Food and Agricultural Sciences (IFAS), this evidence was based on spiders in crowded lab settings.
Tradition also holds that the black widow is a highly venomous and even deadly spider to humans. This too has been overstated, according to IFAS. Their bite can be painful, causing symptoms such as intense pain, muscle cramping, malaise and vomiting, but human deaths from black widow bites are extremely rare. While black widow spiders are native to North America and comprise two closely related species - the northern black widow and the southern black widow, which calls Florida home – the brown widow is believed to be native to Africa. They have been introduced on all continents, with the first documented appearance in Florida in 1935. Though sharing a name associated with aggression and venom, reports of brown widows biting humans are extremely rare. When they do occur, their venom causes less severe reactions to humans than black widows.
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We have established brown widow behavior as being highly aggressive towards the southern black widows, yet much more tolerant of other spiders within the same family. -Louis Coticchio
