Diluted tortoiseshells are called broken colours, and diluted tortoiseshell-and-whites tricolours. It belongs to the family Nymphalidae, which also includes the tortoiseshells and the admirals. Ravens are most common to prey on California tortoiseshells in population explosions during outbreak years. For other butterflies named tortoiseshells, see the genus "Aglais". Male tortoiseshells are rare and are usually sterile. Nymphalis, commonly known as the tortoiseshells or anglewing butterflies, is a genus of brush-footed butterflies. Aglais is a Holarctic genus of brush-footed butterflies, containing the tortoiseshells. In the United States, tortoiseshells are sometimes referred to as "money cats". Tortoiseshells are also known as calimanco or clouded tiger cats, and by the abbreviation "tortie".