Both N. sappho & hylas have the cell bar fractured (like a broken bone)& underside with the white band edged in black.

N. hylas has the FW postdiscal spots elongate & the HW white band's lower border with a tiny triangular spot (at the base of space 3).
N. sappho has the FW spots more rounded & the HW basal spot 3 often absent; Underside ground is a deeper rusty brown.