Wasps on Runner Beans?

[Duke Ellington]

I have noticed that there are quite a few wasps congregating on my runner beans!! sometimes four or five huddled together on one bean. Does anyone know why ?

Duke

[Duke Ellington]

[tonybloke]

2 possibles, 
1, eating a caterpillar.
2, they are lost (nest dying)

[OllieC]

Had them buzzing around my PSB today - a truly beautiful sight. They can only be eating caterpillars or aphids - either way they're my friends!