Original: Mulberry leaves, particularly those of the white mulberry, are ecologically important as the sole food source of the silkworm (Bombyx mori, named after the mulberry genus Morus), the pupa/cocoon of which is used to make silk.
Simplified: Mulberry leaves, particularly those of the White Mulberry, are also important as food of the silkworm, the cocoon of which is used to make silk.