Ladybird, Ladybird

I can never see one of these without the nursery rhyme popping into my head :

Ladybird, ladybird fly away home,
Your house is on fire and your children all gone,

Like many such rhymes it seems unnecessarily  cruel and its origins and meaning (if it had one)  are lost in the mists of time.    But such rhymes have a powerful hold on those of us who heard them when young and never forgot them.