本文欲由「建構論」出發，說明「害蟲」實為 19世紀下半葉才慢慢在東亞出現的新概念和新語彙。以臺灣為例，後世被認為危害甚烈的「螟」蟲，雖然明清時期的文獻記載甚夥，但多半集中在轉化為比喻養子的「螟蛉子」風俗，而與農害無涉。今人或以為清朝無「科學」知識，故對蟲害無所知覺，然若執此一端，則輕忽了其間隱含的觀念變化。由「螟蛉」轉為「螟害」，正是日本殖民統治下，將「害蟲」這個概念傳入後而來。近代國家的出現，殖民統治、都市化、戰爭需求，以及近代農學知識的轉型與應用昆蟲學的形成等多重因素的交會，才逐漸產生「害蟲」的概念。日本殖民統治臺灣時期，「蟲害」發生的頻率和種類不斷增加，實因應用昆蟲學讓原本早已存在於臺灣的昆蟲轉為害蟲。面對這些重新被界定、挖掘出來的害蟲，殖民政府透過制度的力量，包括頒布害蟲預防法規，設立農業試驗場、植物檢查所以及害蟲巡視員等組織，試圖防堵壓制「害蟲」對農作造成的損失。 1920年代以降，日本化學工業突飛猛進，無機及有機化合物製成的農藥開始大行其道，臺灣的應用昆蟲學專家也不遺餘力地介紹各式新農藥產品。不過，農藥在不同農作物的應用情形並不一致，臺灣只有在柑橘瓜果等進入國際市場的農作物採取了「先進」的劇毒農藥，食糧作物中的水稻則仍維持傳統的人力防除法，而與日本國內廣泛使用農藥的趨勢不同，這或許是殖民地與母國在都市化及農業商品化速度不同的表現。

This paper argues that the concept of “pest” in East Asia is a constructive idea that gradually emerged from the late nineteenth century. Take Taiwan for example; there are a lot of records from the Ming and Qing period concerning the moth. However, in contrast to the identification of the moth as pest in the twentieth century, most of these older records describe the moth (or mulberry insect, mingling, 螟蛉) as the adopted son (yangzi), a metaphor originated from the Book of Odes, which is irrelevant to the notion of “pest”. To simply criticize our predecessors lack of “scientific knowledge” would disregard the subtle transformation of the concept from “moth” to “pest.” In fact, “pest” was a novel idea introduced into Taiwan during the Japanese colonial rule. Six factors contributed to the emergence of “pest”: the birth of the modern nation-state, colonial control, urbanization, industrialization, preparation for war, and the emergence of scientific agriculture and entomology. With this new perspective, new pests were incessantly “discovered” by Japanese entomologists and the frequency of pest damage was ever and increasingly growing. Alarmed by the damage and loss of agricultural productivity caused by such pests, the Japanese colonial government tried to prevent and control the pests by the following institutional and administrative measures: issue regulations for preventing and eliminating the pests, establish agriculture laboratories and quarantine stations, and organize “pest patrols” to monitor and warn about potential pest damage. Thanks to the enormous strides of the Japanese chemical industry during the interwar period, organic and inorganic pesticides were widely adopted by Japanese farmers, and the entomologists concomitantly introduced pesticide products into Taiwan. However, the degree of pesticides application varied widely in different agricultural sectors in Taiwan. As an international commodity, oranges, for example, were heavily fumigated with poisonous cyanide gas; but pests in paddy land were continuingly treated by manual and labour inputs, which was quite different from their Japanese counterpart, who intensively applied various chemical pesticides. This variation and difference indicates a sharp contrast between Japan and Taiwan, and reflects the different effect of urbanization and agricultural commercialization in the two places.