A large suspension bridge that spans Ohio's Scioto River has got its Halloween look all wrapped up – thanks to thousands of orb-weaving spiders that have enveloped the structure with their intricate webs.

How many spiders are we talking about? David Shetlar, an entomologist with Ohio State University, estimates that as many as 10,000 of the arachnids have set up their webs on the bridge's hand and guardrails – so many that in some places the delicate webs actually overlap.

The bridge might look suitably spooky, but there's a pretty practical reason for the invasion. “It’s the night lights [on the bridge]. All the midges, mayflies and caddisflies go up to the lights. Spiders aren’t dumb – they go to where the food sources are,” Shetlar tells The Columbus Dispatch.

The spiders, which include arabesque and long-jawed orb-weavers, do their hunting at night, and can be seen repairing their webs by daylight. The shape of the bridge guardrails makes them ideal for arachnid encampment, but there's another positive explanation for why the spiders have chosen this spot: the area has been given a boost thanks to a multimillion-dollar riverfront greening project.

“There is more insect life. And that spawns the spiders. If they don’t have things to eat, they are not going to be there," explains Jim McCormac from the Ohio Division of Wildlife.

Since adult spiders can withstand pretty chilly temperatures (as low as 20°F or -6°C), the bridge's new residents are likely to hang around well past Halloween, at least until a hard freeze hits.  

Top header image: Susan Ujka's Collection, Flickr