120. The Straight Pierrot (Caleta roxus roxana)

Number: 120
Family: Lycaenidae
Sub-Family: Polyommatinae
Species: Caleta roxus roxana
Common name(s): The Straight Pierrot
Rarity: Unommon
Province(s) / Place(s) sighted: Phu Wiang NP (Khon Kaen); Kaeng Krachan NP

Here's a brown specimen I saw at Phu Wiang NP. Anyone know why it is brown?