Tritomegas species
This is the larva of a Tritomegas species. We haven't been able to establish yet whether this is Tritomegas bicolour or Tritomegas sexmaculatus. T. bicolour would be our first option as this is the more common species of the two. The adults are black and white and do look like the Cabbage Bug. As far as we can see on the web neither are British species. Still, if you think you can solve the riddle, please let us know. The animal is more than welcome in the garden, though. After an explosion of saw fly larvae on our roses, this bug larva appeared and killed most of them very quickly indeed. That's how we like our bugs to behave...
