The two-spotted spider mite,Tetranychus urticae Koch has two forms:green form and red form.Understanding the molecular basis of how these two forms established without divergent genetic background is an intriguing area.As a well-known epigenetic process,DNA methylation has particularly important roles in gene regulation and developmental variation across diverse organisms that do not alter genetic background.Here,to investigate whether DNA methylation could be associated with different phenotypic consequences in the two forms of T.urticae,we surveyed the genome-wide cytosine methylation status and expression level of DNA methyltransferase 3 (Tudnmt3) throughout their entire life cycle.Methylation-sensitive amplification polymorphism (MSAP) analyses of 585 loci revealed variable methylation pattes in the different developmental stages.In particular,principal coordinates analysis (PCoA) indicates a significant epigenetic differentiation between female adults of the two forms.The gene expression of Tudnmt3 was detected in all examined developmental stages,which was significantly different in the adult stage of the two forms.Together,our results reveal the epigenetic distance between the two forms of T.urticae,suggesting that DNA methylation might be implicated in different developmental demands,and contribute to different phenotypes in the adult stage of these two forms.