Transcriptomic Characterization of miRNAs in Pyrrhalta aenescens Fairmaire in Response to 20-Hydroxyecdysone Treatment Pyrrhalta aenescens, a major pest of elm trees, causes extensive ecological and economic damage through rapid population growth and defoliation. Existing research mainly focuses on its biological traits and chemical control, with little knowledge about its reproductive development mechanisms, a key factor in population expansion. In other insects, the steroid hormone 20-hydroxyecdysone (20E) regulates development and reproduction via microRNA (miRNA)-mediated pathways, but this has not been studied in P. aenescens. This study aimed to systematically identify miRNAs responsive to 20E in P. aenescens and unravel their roles in regulating reproduction and metabolic pathways, providing foundational insights into hormone–miRNA crosstalk in this ecologically significant pest. Adult beetles (collected from Baotou, Inner Mongolia) were injected with 1.0 μg/μL 20E or control. ...