Complex sentence: Traditionally, the Hesperiidae are placed in a monotypic superfamily Hesperioidea, because they are morphologically distinct from other Rhopalocera (butterflies), which mostly belong to the typical butterfly superfamily Papilionoidea.
Split into simpler sentences: Traditionally, the Hesperiidae are placed in a monotypic superfamily Hesperioidea. This is because they are morphologically distinct from other Rhopalocera (butterflies), which mostly belong to the typical butterfly superfamily Papilionoidea.