The Stygian River Cave in southern Indiana is home to a minuscule species of spiders that science has only just recently found out about. The tiny arachnids measure just two millimeters (or about 0.07 inches) in size and belong to a genus of spiders called Islandiana, commonly referred to as sheet weaver spiders.
As revealed by their moniker, these microscopic crawlers — also known as dwarf spiders or money spiders — weave sheet-like webs that are flat and horizontal.
The new discovery is credited to Dr. Marc Milne, an arachnologist at the University of Indianapolis in Indiana, who told Gizmodo what the sheet weavers’ webs look like.
“In the morning when there’s dew on the grass, and you see the little horizontal webs — those are sheet webs.”
Prior to this discovery, the Islandiana genus was believed to be comprised of only 14 species. The newfound spider species is now No. 15 on the list and the first one to be added to the Islandiana group in more than three decades, reports Science Daily.
This previously unknown spider species was hiding out deep within the damp and muddy cave near the Ohio River and had been living there unbeknown to us all until it was discovered by Milne.
This is the fifth species of Islandiana found to dwell exclusively in caves and, so far, it appears to be endemic to this single Indiana cave since no one really knows if these spiders exist anywhere else in the world.
Described in a new study published in the journal Subterranean Biology, the miniature critters have slightly translucent bodies colored in a “dusky yellow to tan” hue and sport black circles around their eyes.
“These specimens were largely found in webs in between the large boulders within the largest room of the cave,” Milne explained in his study, illustrated by Elizabeth Wells, an alumnus at the University of Indianapolis.
The scientist was initially alerted to the presence of the spiders inside Stygian River Cave by fellow arachnologist Dr. Julian Lewis. To return the favor, Milne and Wells decided to name the new spider species Islandiana lewisi, “in honor of our friend and colleague.”
Collected in October 2016, the Islandiana lewisi specimens seemed intriguing right from the very beginning, said Milne.
“I didn’t know what the spider was at first, I just thought it was odd that so many were living within this dark cave with no other spider species around.”
According to Science Daily, the scientist originally misidentified the new sheet weaver species and it was only months later, after a close look under the microscope, that he realized he had actually discovered a previously unknown arachnid.
Islandiana lewisi is probably “harmless to humans” and most likely preys on springtails and other tiny arthropods.
Commenting on the new find, Milne told Gizmodo that surprising discoveries can be made anywhere on the planet, including the unlikeliest of places.
“When people think of new spiders being discovered, they think of the Amazon or the ice underneath Antarctica. But even in our backyard, there are a lot of new, undiscovered organisms that we don’t know much about.”