A biology professor in northern British Columbia has spotted a clover field crawling with spiders.

Brian Thair of the College of New Caledonia in Prince George said he saw a silky, white web stretching 60 acres across a field.

"When you see horror movies with spider web festooned from this place to that place and so on, it comes nowhere near approaching what occurred in this field," Thair told CBC Radio's As It Happens.

A typical barbwire fence on wood posts surrounded the field about six kilometres east of McBride in the Robson Valley. Thair said it looked like the whole area was covered with an opaque, white plastic grocery store bag.

The thin, elastic coasting was not soft and fluffy like webs built by individual spiders. There were about two spiders per square centimetre laying the silk, which first appeared in early October.

Thair said the web showed great tensile strength enough to put a handful of coins on it without them falling through.

Crazy ideas proposed to explain web

There were "in the order of tens of millions of spiders running frantically back and forth," but they weren't interacting with each other.

Since the spiders didn't seem to care if an occasional insect stumbled into their construction, Thair doesn't think it was built for trapping purposes.

He suggests the spiders encountered an enormous quantity of high quality, nutritious prey to be able to accomplish this feat.

But he's also heard other suggestions.

"Some people have said, 'oh yes, well it's a trampoline for aliens,'" Thair joked. "Or maybe it was an effort collectively by these spiders to try and catch a sheep."

Snowstorms and wind have blown away much of the web since he first spotted it the week of Oct. 27, but Thair intends to return to the field to see if the spiders have mated successfully.