I swear by Ortho Home Defense. We used to get swarmed by ants in our old pop up, and sometimes also had spiders who would make it their home as well. We also had spiders and ants in our second camper (travel trailer). I sprayed that in the spring and *poof* no more pests for the rest of the season.
I've also used it around the house and it's great stuff. We used to live in the woods and had huge numbers of HUGE spiders that would casually stroll in and sit down on the couch next to us (okay, just kidding, but they were very, very big), as well as centipedes and other nasties. I'd treat with this and be pest-free for a long time.
If you use it, spray and allow to dry completely before allowing people/animals in the area.
2015 Jayco JayFlight 33RLDS - Elite package
2010 Chevy Silverado 2500