a lemon emigrant (catopsilia pomona) locked in a closed store at central.
it is a swift flyer and likes to visit flowering plants, well, back in its normal world. the patches on the wing say that it is in form catilla.
粉蝶科 pieridae family (whites, yellows)
郊野情報蝴蝶篇（第二版）hong kong butterflies (second edition) isbn 988-201-631-6