I havent had any ant's in my trailer but did have an ant issue in my kitchen once - I bought some Terro Liqued Ant Baits and put them on the window sill - they were gone in less then a week.
I would do a Bug Bomb (verify it say's ants too) if you suspect them in the walls - make sure to take any food and or dishes out to minimize the cleaning up after the bomb and make sure you have no gas or electric "on" the trailer and then once the Bomb is done you can air out the trailer for a few hours to get rid of the smell.
2011 Rockwood Mini Lite 2306 - Matt
2004 Dodge Ram 1500 Qaud Cab 4x4 with 35" tires and 3.92 gears, Dynatech Longtube Headers & Fabtech 6" lift + Superchips with shift Tuning
Nights Camped 2011 (37) - 2012 (16)-2013 (2) -2014 (5) -2015(0)
USMC 91 - 95 - F/A-18 Aviation Ordnance