Last night I inspected my hive. I pulled three bars.

When I pulled the first two (#3 & 7, near the entrance) everything was fine. The bees were happy to see me, we had a nice conversation, etc. etc.

When I pulled the last bar (#12 from the entrance) they scrambled the jets. Several bees came flying out at me, and they were ticked off.

No difference as far as I can tell regarding handling.

Any thoughts on what causes the difference in behaviour?