What turns bees nasty

[Swarm]

I inspected mine earlier and they were lovely, but if I went back again tomorrow, I'd expect them to be different.

 

[Galaxy55]

Around my apiary the June gap, when food is scarce I feel has an impact on temperament. Noticeable this year for the first time for me.

 

[Finman]

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There are beestocks which are always calm. They are nice to nurse.

 

[Karol]

I looked at my colonies on Thursday. One colony fine and not angry. The rest absolutely terrible!
Weather hot and humid but tons of nectar going in. Normally quiet colonies became very aggressive.
Clean suit but hands and arms were main target. Then thought would I be happy if someone broke into my houses and raided my food store and tipped up all my belongings. NO!

Was the first colony fine and then the rest angry?

Might be that you picked up bee proteins from the first hive on your hands and sleeves and with hive stores building you might then be perceived as a robber by the subsequent hives?