Iona Opie, who has died aged 94, was, with her husband Peter, one of the world's greatest experts on the folklore, games and beliefs of childhood; the Opies' study of children's culture, The Lore and Language of Schoolchildren (1959), described "the greatest of savage tribes – the worldwide fraternity of children" – a society that few people until then understood or even realised existed. The Opies began their quest out of curiosity about the origins of nursery rhymes. Shortly after they got married in 1943, they saw a ladybird during a walk in the countryside. Recalling the rhyme "Ladybird, Ladybird, fly away home", they wondered where it had originated and discovered that the only available anthology of nursery rhymes had been published in 1842. "Ladybird, Ladybird", for example, is known in some form more or less everywhere – including China. Humpty Dumpty is "Boule Boule" in France, "Lille Trille" in Denmark and "Humpelken Pumpelken" in Germany.