Ants!

A creepy real estate broker checks into the old fashioned Lakewood Manor, intent on fleecing the owner out of the property to replace it with a casino. His plans are foiled when several hundred thousand uninvited guests arrive (without reservations) in the form of poisonous ants disturbed by the casino construction. Guests and employees are trapped in the hotel and pushed floor by floor upwards by the ants' unrelenting march.