Dr. John Styrsky hasn’t always been a fan of spiders.
“Actually, spiders make me really uncomfortable,” the University of Lynchburg biology professor admitted recently. “Something about the number of legs they have and the way they move them gives me the heebie-jeebies, so I typically give them a wide berth.”
But there was something about two kinds of spiders he encountered in Panama in the early 2000s that made him want to take a closer look.
A doctoral candidate at the time, Styrsky was in the Central American nation researching birds when he saw two species of orb-weaver spiders that live on the acacia, a tree also known as the “bullhorn acacia” for the steer horn-shaped thorns or spines that grow on it.
“The acacias are the ‘host plant’ for the spiders, meaning the spiders have a preference for [them] or are only found on the acacias,” Styrsky said.
“There are a few documented examples of spiders that are ‘host-plant specific,’ but this host specificity is very rare, particularly in the large family of spiders called orb weavers, the spiders that make the spiral-shaped webs people see.”
The orb weavers aren’t the only creatures inhabiting the acacias. The trees are also home to an aggressive species of ants with a fitting scientific name: Pseudomyrmex satanicus. As Styrsky puts it, “When they swarm and sting, it’s like having the wrath of Satan visited upon you.”
The ants hollow out the acacia’s thick thorns, using them as nurseries for their young. They also eat the sugary nectar secreted by the plant. In exchange for lodging and food, the ants aggressively defend the acacia against anything that might want to eat or even touch it — anything, that is, except the orb-weaver spiders, which for reasons not yet clear, get no grief from the ants.
For their part, the spiders leave the ants alone, too. “They are not predators of the ants,” Styrsky said. “They sit on their webs at night to capture flying insects, but during the day they rest crouched against the surfaces of the leaves, stems, and thorns, unmolested by the ants.”
He added, “These interactions had never before been documented, so I was eager to get back down there once I graduated and study them.”
In 2007, Styrsky returned to Panama, where he discovered that Dr. Thomas Hesselberg, an Oxford University scientist, was also researching the spiders. “[He] had started a post-doctoral project investigating web-building flexibility in one of the two spider species,” Styrsky said.
“We happened to run into each other at the Smithsonian Tropical Research Institute in Panama City and then spent some time in the field together. His research focus turned back to England, but we kept in touch over the years.
“Last year, he got the bug to return to Panama, so he reached out to me about collaborating with Dumas Galvez, an ecologist at the University of Panama who was interested in our work. From there, we started putting a grant proposal together.”
Galvez, Hesselberg, and Styrsky recently received a $120,000 grant from the Republic of Panama’s National Secretariat of Science, Technology, and Innovation, a government agency comparable to the National Science Foundation in the U.S.
The two-year grant, “Host specificity, chemical mimicry, and dispersal behavior in acacia orb-weaver spiders,” will fund travel expenses, equipment, and chemicals, and will also enable university students, including one from Lynchburg, to participate in the research.
Between 2008 and 2014, Styrsky took six Lynchburg biology majors to Panama to study the acacia orb weavers. With the grant — $5,000 of which is set aside for Lynchburg — he will return to Panama with one student, likely in the summer of 2023 or 2024.
“The grant money earmarked for Lynchburg will cover travel and housing costs and provide a small stipend for a student,” he said.
Working with researchers from Panama and Oxford, Styrsky and his student will try to explain, among other things, how this ecological “odd couple” coexists on the acacia.
“So far, my students and I have determined that [the spiders] are behaviorally adapted to avoid ant detection and attack,” he said.
“As long as they remain perfectly still, the ants don’t seem to notice them, even if they walk right over them. The spiders also tend to rest on parts of the plant that have the greatest ant density. It is also possible that the spiders are chemically camouflaged.
“They may absorb the odors of either the plant or the ants, making them ‘invisible.’ This is one of the hypotheses we will address as part of the grant.”