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Please can anyone tell me what this insect is? It's eating my Swiss Chard (Silver Beet). Thanks very much.

Is it  a Shield Bug?

http://philhutt.com/USERIMAGES/BUG%20SHIELD%20BUG%20IMG_8066.JPG

I'd be interested to know what these are too and what damage they do as I spotted two of them sitting on rhubarb leavings mating!

Shield bug. I get them all over the plot. They're vegetarian, but they don't seem to damage anything. Something's been at the chard, but I don't think the odd shield bug ate all that!

Could it be pigeon damage?
Ive grown swiss chard for three years & never had to cover it or protect it at all. It has been pretty indestructible but for some reason this year the pigeons have been attacking it  :o
I actually saw them doing it & had to chase them away. Ive got no idea why they are suddenly interested in it except maybe its because I am getting much better at covering/protecting my brassicas, fuits etc & the chard was the only unprotected item on my plot at the time