Bugs on Runner beans - friend or foe

I have just been down the garden to have a chat with my runner beans and there were a few bugs on them that I didn't recognise. There were the usual blackfly and a variety of different coloured and spotted ladybirds - who do a good job of controlling the blackfly.

This new bug - too small for my camera to show it - is about 1 cm long and very slightly oval. It has a solid shape similar to a ladybird but not round and not segmented. The head end is black and the rest of the body is bright green. On the bright green part there are three lines running across the body and they look almost like vents or gills. They could be just markings but they are too small to be sure - I'll take a magnifying glass next time.

Any ideas?
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shiney

 

Webmaster moved my topic to here - maybe the right person will see it now.
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shiney

 

Thanks Maggie/chips

My bugs aren't quite the same as their bodies are bright green. I haven't seen them for over two weeks and the plants seem undamaged so I stopped worrying. I hope your fuschias are OK.
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shiney