Bait Hive intruders

[mike99]

I tried to capture any local roving swarm that might be looking for a new home by leaving a Nuc in the garden. I had nowhere to raise it more than 1m but I have had no luck so far. However, the last few days I have lifted the lid of the Nuc and a bumble bee would emerge. There are frames with drawn comb in but no honey in the Nuc. Any ideas of what this bee is doing?

 

[Millet]

My bet is the smell of the drawn comb is attracting the Bumble bees which may have the smell of nectar/honey in them.