YES! You need to S.O.S. (seek out the source). There could be a leaky pipe (or similar situation) that created an area for them to breed in and thrive. Once you find the source, a labeled insecticide for that site will work. After that, I'd recommend getting a "good" bacteria containing drain cleaner. I use a product called Drain Gel, and apply it to all drains monthly. It can be found at DIY pest control online stores.