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Melanization is a common phenomenon in insects, and melanin synthesis is a conserved physiological process that occurs in epidermal cells. Moreover, a comprehensive understanding of the mechanisms of melanin synthesis influencing insect pigmentation are well-suited for investigating phenotype variation. The Asian multi-colored (Harlequin) ladybird beetle, <i>Harmonia axyridis</i>, exhibits intraspecific polymorphism based on relative levels of melanization. However, the specific characteristics of melanin synthesis in <i>H. axyridis</i> remains elusive. In this study, we performed gene-silencing analysis of the pivotal inverting enzyme, tyrosine hydroxylase (TH), and DOPA decarboxylase (DDC) in the tyrosine metabolism pathway to investigate the molecular and regulatory mechanism of melanin synthesis in <i>H. axyridis</i>. Using RNAi of <i>TH</i> and <i>DDC</i> genes in fourth instar larvae, we demonstrated that dopamine melanin was the primary contributor to the overall body melanization of <i>H. axyridis</i>. Furthermore, our study provides the first conclusive evidence that dopamine serves as a melanin precursor for synthesis in the early pupal stage. According to transcription factor <i>Pannier</i>, which is essential for the formation of melanic color on the elytra in <i>H. axyridis</i>, we further demonstrated that suppression of <i>HaPnr</i> can significantly decrease expression levels of <i>HaTH</i> and <i>HaDDC</i>. These results in their entirety lead to the conclusion that transcription factor <i>Pannier</i> can regulate dopamine melanin synthesis in the dorsal elytral epidermis of <i>H. axyridis</i>.