Found in Tai Tam Country Park in Tsuen Wan (Shing Mun reservoir) the third week of August, 1998.  With several Common Bluebottles (Graphium sarpedon), it was sipping water (probably laced with urine) on a concrete bridge foundation block.  While this species is common in Guangzhou, China, it is just now making its way into Hong Kong.  Wingspan is about 9 cm / 3.5 inches.

This is a male specimen.  Note the typical (for Graphiums) featherlike pheromone brushes carried in folds of the inside edges of the hindwings.  (To see more clearly, right click on the first image and select:  View Image.)