The second part of The Butterfly Trail is Wu's travelogue of Taiwan's lepidoptera and their habitat. He also explores past and present conceptions of the natural world among different ethnic groups.
《蝶道》的下半卷「行書」則是吳明益的島嶼行旅，書寫他觀察台灣蝶類的第一現場，從而探討不同族群、時空下，不同自然概念在台灣島上留下的新舊交雜歷史遺痕。