Abstract: Insect wing polyphenism, as a typical example of the developmental plasticity of organisms, is the result of evolutionary adaptation to complex and variable environments. The brown planthopper (BPH), Nilaparvata lugens, is a representative model of insect wing polyphenism, and its nymphs have the option of developing into shortwinged or longwinged adults. The ability of developing into longwinged morphs enables BPHs to migrate over long distances, causing an infestation over a wide geographic rice planting area in Asia. Since the 1960s, there has been extensive research into the mechanisms behind wing polyphenism in BPHs, revealing that numerous environmental factors such as population density, host plant quality, temperature and photoperiod, and juvenile hormone can all influence the proportion of wing morphs. In the past 20 years, facilitated by the rapid development of biotechnologies in genomics, RNAi and gene editing, a breakthrough finding has been achieved in wing polyphenism of BPHs. FoxO has been identified as a switch gene for wing polyphenism in BPHs, where silencing or knocking out FoxO leads to the development of long-winged adults. Meanwhile, the insulin signaling pathway can inhibit FoxO from entering the nucleus by phosphorylating it, thus participating in wing polyphenism regulation. The zinc finger transcription factor Zfh1 can regulate the transcription of FoxO through promoter binding, paralleling the insulin signaling pathway in controlling wing polyphenism. Another zinc finger transcription factor, Rotund, can interact with FoxO to co-regulate wing polyphenism of BPHs. Additionally, the sex determination gene Transformer-2 and the c-Jun N-terminal kinase pathway can also influence wing polyphenism, indicating the presence of diverse molecular regulatory mechanisms for wing polyphenism in BPHs. Given the differences in the mechanisms of wing polyphenism among different suborders of Hemiptera, the elucidation of mechanisms in BPHs is far from fully explaining the mechanisms of wing polymorphism in Hemiptera or even the entire class of insects. However, these findings position themselves at the edge of wing polyphenism in insects and deepen our understanding of developmental plasticity and evolution of insect wings as well as other tissues.

Key words: Nilaparvata lugens, Hemiptera, wing polyphenism, phenotypic plasticity, juvenile hormones, transcription factor