Pale marks on the head of A. papillosa are frequent in America where A. filomenae is absent, though in the Pacific the Californian A. loui has marks which can cause confusion where its range overlaps northwards with that of A. papillosa. The mark in America usually resembles a wine glass (1), sometimes partly overlaid by freckles of pigment (2) and sometimes centrally faded with small lateral branches which approximate to a Y (3), but the branches usually bend to meet at an obtuse angle of nearly 180° instead of the acute junction of the arms of a Y.
1: Alaska, July 2013. © E. McKittrick. 2 & 3: Maine, USA, December 2021. © J. Goddard.