Although I recognised this larvae as a ladybird species from shape, the markings are different from the mauve and orange ones I recall from long ago. Online reseach reveals they are the larvae of the Harlequin ladybird, which was introduced, or possibly not, to the UK as a biocontrol. Why does this make me think of Grey Squirrels?
Ladybird sightings can be recorded at this link where an image can be uploaded so a proper expert can identify and verify the species.
There is no guidance whether to intervene and remove them so they are still munching away on the blackfly.
Harmonia seems an odd name for something that does not appears to be very harmonious to our native species.
Ladybird, ladybird fly away home,
Your house is on fire and your children all goneTrad
The ‘house on fire’ is thought to refer to the traditional practice of burning off the stubble after harvest. This conjures images of leaping flames but the reality of my younger years was far more low key with somebody dragging a something around the field that caused the stalks to burn and singe. Sometimes afterwards the stubble would be ploughed into the soil. The practice has been discontinued for a number of years.