I autumn-fed all my hives with syrup this afternoon and […] robber bees were attracted to the smell. All fought off the attacks off easily within a few minutes, but the hive with the Upstairs Downstairs set-up seemed to lockdown and protect itself with much less drama."
Nothing over 7mm gets into this hive:
Wasp, hornet, wax moth, rodent or reptile
Giving back to bees a hive they know how to defend