Adenosine-to-inosine (A-to-I) RNA editing is site-specific modification of RNAs that increases the diversity of the transcriptome and proteome. Most insects undergo complete metamorphosis, including four life cycle stages: egg, larva, pupa and adult. Many previous studies have confirmed that RNA-editing events occur in a development-specific manner; in other words, RNA-editing levels change during metamorphosis. Here, we describe an effort to identify the developmental specificity of RNA-editing events using a large-scale computational analysis of RNA-seq data derived from four developmental stages of the diamondback moth, Plutella xylostella. One thousand one hundred and eighty-seven A-to-I RNA-editing sites were predicted to be developmental stage specific (false-discovery rate <0.01) and 1,094 of these sites were located in protein-coding regions. Editing of 152 sites resulted in an altered amino acid residue. A putative adult-specific A-to-I RNA-editing site was verified by comparing cDNA sequences with its corresponding genomic locus at different stages of the P. xylostella life cycle. Our findings will help elucidate the role of A-to-I RNA editing in the regulation of metamorphosis. Further studies detailing changes in the extent of editing are needed to establish how as yet unknown regulatory factors are involved in the editing mechanism and what biological functions' editing serves.