If you are seeing a "dropping" that looks kind of like coffee grains in a little pile, you MIGHT have the species of Drywood Termites. They can "come & go."
To confirm, take some droppings to the local Agricultural Extension office for a positive I.D. (Usually free and unbiased) There are other insects that leave a similar dropping so identification is critical.
If they are Drywood Termites, the chance of do it yourself treatment are very low and ill advised. The problem is this species remains hidden deep in the wood and if found in one location are often hidden in other locations you will never find until the wood collapses.
You can use heat or fumigation. The most common occupancy time is 72 hours, although by adjusting the dosage,(and increasing the cost) it can be completed in as little as 12 hours.
I am also very familiar with the heat method also, and I have to say I would not use heat if it were my RV.