Taxpayers are on the hook for an $18,000 fumigation of a federal government building in what turned out to be a false sighting of a rare venomous spider.

In June, the Shared Services Canada building in Ottawa had to be evacuated after employees said they saw a brown recluse spider, a potentially dangerous arachnid that is extremely rare for the region. The 50 workers were sent home for two days.

Another spider sighting on Oct. 18 prompted a second evacuation. The spider was caught this time around, but while employees waited for the results on the arachnid, management decided to fumigate the building.

"Because the health and safety of our employees matters, while waiting for the analysis on the spider from the lab, management decided to clean and treat the ducts and fumigate,” Shared Services Canada said in an emailed statement to CTV Ottawa.

As it turns out, the spider was a yellow sac spider, which is much more common for the area and not seriously harmful to humans.

Dr. Chris Buddle with McGill University’s department of Natural Resource Sciences believes the steps the government took to eradicate the spider were a waste of money.

“I don't doubt that there were spiders there and I also don't doubt spiders freak a lot of people out … but I don’t think fumigation or evacuation is the right response,” he said.

“Spiders in homes are generally a good thing. They'll eat a lot of other critters that we like even less than spiders.”

Buddle said he’d prefer the money be spent on an awareness campaign teaching people the benefits of having spiders indoors.

With a report from CTV Ottawa’s Joanne Schnurr