The Lemon Migrant takes two seasonal forms, the 'dark form' in our wet season and the 'light form' for the rest of the year. The defining difference, according to Braby, is antennae colour; it's not the most obvious difference at any distance(!) but gets around the fact that wing coloration of both forms is rather variable. This is a dark form male; female is adjacent. See www.flickr.com/photos/malcolm_nq/4951181434/
and nearby for the pale forms.