The Asian Hornet is said to attack honey bee colonies. In any case, non native species can cause severe disruption to the local ecology.
The late swarm which I caught at the end of July has settled in. It appears to be vigorous and there were many bees flying today. I noticed that they were darker and smaller than I remember from the collection.
It may have been the overcast day which made them look darker. I may be mis-remembering. Seven weeks have passed since I caught the swarm so it's possible that these are new brood.