Mud Daubers/Hornets/Wasps

They eat spiders so spiders must be about. You asked!

These critters have an attraction to propane. The first thing to add to your new TT as summer approaches is a screen over your furnace vent to keep them out. Various shapes are available at most RV and camping supply dealers to fit your RV. Gas grills have the same problems, but, with them it is often with spiders crawling up the lines causing blockage. Who knows why. Perhaps the little buggers get high on the propane fumes. Carefully clean out the vents and add a screen and all should be OK.

Can't answer the 'why' but I get them in the same places. I spray their nest with the Raid for that purpose (for the furnace intake, I refrain from using the furnace for a while but I dismantle the nest and pull it out--or vacuum it out--once I'm sure the hornets are dead). This takes care of the problem--at least until next year. ;-) How to prevent them? Wish I knew!