They could just be collecting there because its the warmest spot in the trailer with the least amount of airflow. Also, the bottom and sides of that bunk area are open to the storage area below. I would start by taking off the inspection panels and looking into the walls around the bunk area, and flip up the bottom bunk and closely inspect the storage area below. Also, closely inspect those windows in the bunks for any leaks; they may not be letting in water, but the bugs can still get in.
Let us know what you find!
Edit: Do your little ones have a habit of taking food to bed with them? I might start by stripping the bunks down to the ply wood and inspecting for whatever the critters might be after.
2014 Jay Flight 28 BHBE
2015 RAM 2500 6.4L HEMI, Tradesman 4x4, 3.73
Blue Ox SwayPro (BXW 1503)
Upgraded from an REI internal frame backpack and a Eureka 1/2 dome tent!