Catopsilia is a genus of butterflies in the family Pieridae, commonly called migrants or emigrants. Wikipedia
Catopsilia pomona, the common emigrant or lemon emigrant, is a medium-sized pierid butterfly found in Asia, Cambodia and parts of Australia. The species gets its name from its habit of migration. Some early authors considered them as two distinct species Catopsilia crocale and Catopsilia pomona.The photos below is the Male Lemon Emigrant