How many spiders does it take to creep you out? 10? 100? How many spiders make an “extreme spider situation”?
The Baltimore Wastewater Treatment Plant put out a call for “extreme spider” help in 2009, when a giant spiderweb covered almost 4 acres of their facility. Scientists eventually estimated over107 million spiders were living in the structure, with densities of 35,176 spiders per min spots.
Greene, Aet al. (2010). An Immense Concentration of Orb-Weaving Spiders With Communal Webbing in a Man-Made Structural Habitat (Arachnida: Araneae: Tetragnathidae, Araneidae). American Entomologist, 56 (3), 146-156.
The immense in their title doesnt really begin to cover it. From the paper:
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 facilitys 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.
Remember, that paragraph was written by 5 mid-career professional entomologists and arachnologists. If they were a bit startledby the size of the web….it was a big freakin’ web.
In someareas of the plant over 95% of space was filled with spider web. The webbing was so dense that it pulled 8-foot long fluorescent light fixtures out of place.
The scientists describedtheirestimate of35,176 spiders/m asmarkedly conservative and representing a minimum volume of spiders, by the way.
Question: do you measure spiders in Metric ShitTons? Or in Imperial ShitLoads?
Either way, it’s an awful lot of spiders.
Giant multi-species webs actuallyaren’t that rare. In 2007, a huge communal spiderweb was reported inTexas, and many of the same spider species were found to be the architects. Megawebs in the United States are usually dominated bytwo spider species, Tetragnatha guatemalensis and Larinioides sclopetarius.
All recorded US megawebs have occurred near water.That makes sense, because spiders have to eat, and midges emerge in huge quantities from water where they breed and live.
So, we really do want these spiders around, even if the concept of them coming together to form a giant webby Spider Voltron is a little creepy.
The alternative is a plague of flies. Happy Halloween.
From the Archive: Some portions of this story appeared on my personal blog in 2010.
Edited Nov. 3, 2014: changelink to paperPDF; The Entomological Society’s journal changed the paper toopen access due to the volume of requests.