ants !!!! lotsa ants !!

I literally had ants in my bathroom shower off & on for almost a year, no where else in the house just the bathroom. I constantly cleaned and bleached it, went through I don't know how much terro, raid, and combat ant bait/traps/spray/etc but they kept coming back. They finally went away when I decided to paint the bathroom & the closet where the plumbing access panel was. After I finished painting I shut the doors to keep the fumes in the room and that's what finally killed them. Hopefully you can find a simpler solution than painting but that was the only thing that worked for me. Good Luck!

Call an exterminator. Terminix is very good.

Ants like warm places and electrical current.
Sometimes they will make a nest in your electical outlets.
I have seen large nests in breaker boxes when the boxes have been pulled out to be replaced.

we had small ants but bought this great stuff at home depot. it was in a tube like a big syringe. i think it was called hot shot. it worked great. not sure about the black ants. worth a try.
if you are on second floor do the people below you have them also?

With the drought, our exterminator says the ants are coming inside looking for water. That might explain the bathroom invasion. But I've found the kitchen counter to be far more popular, You have to clean thoroughly and immediately after every food prep, and seal all food containers. Put Terro out all the time, even when you don't see any ants. If you have monthly spraying done around the baseboards, they still get onto the counters by coming down the walls through the windows and outlets and other tiny openings, but keeping food on a free-standing table (not touching a wall) should work, because ants can't get to the table without crossing a sprayed area.

Forgot to include this in my earlier post. Since you are on the 2nd floor, if the bathroom has an adjoining wall with one of you neighbors, you may want to ask if they are leaving any food out near their side of the wall. A few months after I had finally got rid of my ants I was talking to my neighbor (I live in a townhouse) about it and it turns out that one of their roommates had been leaving open food in their bedroom for months at a time, which of coarse attracted bugs & ants. (gross!) Their bedroom wall was the adjoining wall to my bathroom.

One of the things I finally resorted to in my ant wars over the years in Cane Bay was to use baby powder. Sprinkled it on their trails along base of outside walls. Ants don't like silica which is what baby powder really is; so they avoid going across the powder. Terro seemed to be non-effective most of the time. Baby powder only works when it is dry -so if it rained or got wet had to re-do.

Jumbie