Throwback to that time in 2009 when a spider megaweb took over a whole building.

If you're looking for another catastrophe to put on your 2020 bingo card, maybe you can look to 2009 for inspiration. Warning: if you're arachnophobic, maybe sit this one out—or at least take a deep breath before continuing.

A little over a decade ago, nearing Halloween just as we are now, employees of the Back River Wastewater Treatment Plant in Baltimore found something horrifying in their sand filtration facility. The facility spanned a whopping four acres under the same roof, but had no side walls—allowing for the easy colonization of over a hundred million spiders. The entirety of the building's interior was coated and weaved through with a "mega web." The employees had seen spider infestations in the building since its construction in 1993, but this was on an unprecedented and behemoth scale. The management put out a distress call for help with what they described as an “extreme spider situation."

Pictured: An “extreme spider situation." Image courtesy Entomological Society of America.

Answering the call came the arachnologist Avengers—an "interagency team with expertise in arachnology, urban entomology, and structural pest management"—whose brave exploits in the name of science were published in American Entomologist. The researchers arrived at the scene and documented the surreal infestation. 

Image courtesy Entomological Society of America.

These arachnologists were five well-seasoned and mid-career spider experts, but even they were appalled. Their words from the published study:

"We were unprepared for the sheer scale of the spider population and the extraordinary masses of both three dimensional and sheet-like webbing that blanketed much of the facility’s cavernous interior.

Far greater in magnitude than any previously recorded aggregation of orb-weavers, the visual impact of the spectacle was was nothing less than astonishing.

In places where the plant workers had swept aside the webbing to access equipment, the silk lay piled on the floor in rope-like clumps as thick as a fire hose."

In some areas, over 95 percent of the space was filled with spider web. The silk came down several feet from the ceiling almost everywhere and was thick enough to catch most excretions from the spiders. In some places, the webbing was thick and heavy enough to pull down light fixtures and damage equipment. At this kind of thickness, spider silk can be stronger than steel.

Note the weight of all that web. Image courtesy Entomological Society of America.

The scientists eventually estimated over 107 million spiders were living on the premises. In some spots, the density of spiders reached 35,176 spiders per cubic meter.  (You might be wondering how one counts that many spiders—it's easy, you just count up the legs and divide by eight.)

While a variety of spider species took up residence in the facility, the majority were Tetragnatha guatemalensis spiders (a long-jawed orb-weaver) with Larinioides sclopetarius (AKA bridge spider or long cross spider) as the second-largest group. Pictures of these two handsome types below.

Tetragnatha guatemalensis spiders (long-jawed orb-weaver), image courtesy bugguide.net.
 

Larinioides Sclopetarius, image courtesy bugguide.net.

You might have heard spiders are often territorial and cannibalistic, and that's mostly right. In the case of the Back River Wastewater Megaweb, however, the spiders got along swimmingly. Different species moved freely through neighbor's webs, and boundaries were flexible. The scientists noted that an increase in food supply meant more communal, less competitive spiders. And there isn't a much better place for tons of flies and other insects to live than at a waste-treatment plant by a river.

Image courtesy Entomological Society of America.

Image courtesy Entomological Society of America.

The scientists were ultimately pleased to have found the “Back River Arachnotopia," as they called it, and hoped that "this type of fortuitous, enhanced field plot" would be recognized for its worth in the future of spider studies. But arachnologists would say something sensible like that, and not "burn it all down oh no please it's horrible."

Image courtesy Entomological Society of America.

Did you make it this far? Do you feel that itching on your leg? You deserve some kind of medal.

Unfortunately, all I have are megaweb pictures.

Image courtesy Entomological Society of America.

Are you afraid of spiders? What would be your reaction on finding this kind of megaweb? Do you regret learning about this? Leave a comment!