Aphid farm (Aphis fabae)
We thought the beans had escaped the aphids, then I saw the ants. When you see ants on bean plants you can be pretty sure the aphids aren't far because they'll be being 'milked' for their honeydew excretion - a nice example of symbiosis. Honeybees do the same with the aphids sucking the sap of pine trees bu they at least make honey with
the aphid excretion ;-)
An amazing sight to see the aphids bloating themselves on bean sap with their bums in the air and ants walking over them collecting the honeydew. I think the ant is Formica sp. but not sure...