The hive is the bees’ castle and as the number of hawking hornets increases it is time to reduce the entrance and keep out the hornet. French beekeepers do this in one of two ways. the first is to fit a mouse guard of the castellated type, but the openings have to be sized so that the hornet cannot get through. One of the smallest openings to be found in a guard is sold on Amazon by www.simonthebeekeeper.co.uk but even with that guard the openings are 6.5mm wide and that is a fraction too wide. A solution to the problem is to flatten the tabs on a second guard and overlay one on the other. By coincidence a map pin through the perforations allows one to slide the guards just enough to achieve a 0.5mm reduction and get the desired 6.0mm gap (see photographs above). An alternative solution is to turn a guard upside down and, using a drill bit as a sizing guide, create an entrance lintel, with a height of 6.0 mm. Whatever method you use to create a 6.0mm gap, having reduced the entrance, you must now check the hive and ensure it is secure; any openings, badly fitting supers etc. as well as roofs are open a point of entry for wasps, and it would be a good idea to close any feed holes in the cover board.