Shield bugs are proliferating in the garden. These ones seem to like the tomato plants in particular.

I believe they are Nezara viridula, or Southern Shield Bugs, from the family Pentatomidae. The little family here shows them at various stages in their development: they pass through five different colour-patterned stages called ‘instars’ before transforming into their more familiar all-green adult form. It seems that this type only established itself in England in 2003.

See britishbugs.org.uk and blockhill.co.nz (another Garden Zine of sorts) for more info.