When I was in Kindergarden I used to eat chocolate icing for breakfast o_o (It was so good though D8) So One day I left the can open and when I came back ants were all over da place.
The thing you should of done first was called a terminator. Trust me, it helps. Also Have you ever seen saw dust anywhere in your house?
When you said "They must be living in the walls somewhere" That got me thinking, It may be termites.
Any, termites, whatever.
Just call a bug terminator. May cost some cash but it helps.
_____________________

| Quote: |
RainbowMilly : That's a record. Most kids ever had was 69.. AlisaElric0150 : I know. X3. @ 35bell : -giggle-. |
Youtube~Formspring~Fanfiction