Hot, Bright Cities are Spawning Gigantic Spiders

By Alissa Walker on at

File this one under: Oh HELL no. While we know that our ever-industrialising lifestyles make survival tough for animals like birds and mountain lions, in at least one case urbanisation is helping a species to thrive. Thanks to the artificial conditions we create, our cities are growing ultrafertile megaspiders.

A study by University of Sydney that's featured on CityLab today tracks a particular arachnid named Nephila plumipes, which is famous for spinning giant webs, hence its common name, the golden orb-weaver. The team measured both city and country spiders for a variety of biometric indicators including tibia length and ovary weight, and found that the urban spiders were larger in size, had more fat reserves, and indeed had heavier ovaries. Heavier ovaries = lots and lots of eggs.

Researcher Elizabeth Lowe tells CityLab they think two factors in cities are contributing to the superspider trend. First, the hot microclimates generated by a paved-over metropolis make for a more hospitable environment for spider life, period. But there's another interesting variable: cities are so bright due to artificial light that they attract an abnormally large number of insects to the area. Meaning the spiders never have to go hungry. (However, that contradicts slightly with another study we've covered by UC Berkeley, which claimed that concrete and other hardscape surfaces aren't as good for anchoring webs. Maybe these urban golden orb-weavers are really good at buying real estate.)

Nephila plumipes is just one (terrifying-looking) type of orb-weaving spider, but Lowe thinks you'd see the same pattern in most cities. Now remember, spiders are good—we like them because they eat insects we consider to be pests. But too many extra-large spiders lounging around in their warm urban webs, chowing down on flies, and birthing thousands of giant spider babies is probably not healthy for the natural balance of our cities. And it's also not something I want to start confronting on the street on a daily basis. [CityLab]

Photo by Arthur Chapman