The pear psylla, Cacopsylla pyricola Foerster (Homoptera: Psyllidae), is a serious insect pest of commercial pear crops. The species, which resides on pear trees throughout its life cycle, is rapidly spreading in some regions of the world. Given the life cycle, it is unclear how such a rapid spread has been facilitated. Presently, the population genetic structure of the species including genetic diversity and gene flow was studied to understand the nature of dispersal and field ecology of the species. Pear psylla was collected from several pear orchards in Korea. The 658-bp region of mitochondrial COI gene and the 716-bp long complete internal transcribed spacer 2 (ITS2) of the nuclear ribosomal DNA were sequenced. Unlikely other previously studied insect pests, the COI-based genetic diversity of the pear psylla was extremely low (maximum sequence divergence of 0.15%). This finding allowed us to conclude that the species may have been introduced in Korea relatively recently, possibly with the phenomenon of genetic bottlenecks. ITS2 sequence-based analyses of phylogeny, population differentiation, gene flow, and hierarchical population structure all concordantly suggested that the pear psylla populations in Korea are neither genetically isolated nor hampered for gene flow. These genetic data are concordant with the dispersal of an overwintering winterform morph outside the non-pear habitat in the fall and the possibility of subsequently longer distant dispersal.

The 15,389-bp long complete mitogenome of the endangered red-spotted apollo butterfly, Parnassius bremeri (Lepidoptera: Papilionidae) was determined. This genome has a gene arrangement identical to those of all other sequenced lepidopteran insects, which have the gene order of tRNAMet, tRNAIle, and tRNAGln at the beginning. Due to the uncertainty the start codon for COI gene in insect has been discussed extensively. We propose the CGA sequence as the start codon for COI gene in lepidopteran insects, based on complete mitogenome sequences of lepidopteran insects including our P. bremerii and additional sequences of the COI start region from a diverse taxonomic range of lepidopteran species (a total of 51 species belonging to 15 families). As has been suggested in other sequenced lepidopteran insects the 18 bp-long poly-T stretch and the downstream conserved motif ATAGA that were previously suggested to serve as a structural signal for minor-strand mtDNA replication also was found at the 3’-end region of the P. bremerii A+T-rich region. In an extensive search to find out tRNA-like structure in the A+T-rich region, each one tRNATrp-like sequence and tRNALeu (UUR)-like sequence were found in the P. bremeri A+T-rich region, and most of other sequenced lepidopteran insects were shown to have tRNA-like structure within the A+T-rich region, thereby indicating that such feature is frequent in the lepidopteran A+T-rich region. Phylogenetic analysis using the concatenated 13 amino acid sequences and nucleotide sequences of PCGs of the four macrolepidopteran suferfamilies together with Tortricoidea and Pyraloidea well recovered a monophyly of Papilionoidea and a monophyly of Bombycoidea. However, Geometroidea and Noctuoidea were unexpectedly clustered as one group and placed this group to the sister group to Bombycoidea, instead of Papilionoidea in most analyses.

Invertebrate mitochondrial genome contains 13 protein-coding genes and major start codons for them are ATA (Met) and ATG (Met). However, alternative start codons such as ATT (Ile), ATC (Ile), TTG (Leu), and GTG (Val) also have been suggested from a diverse organism. Approximately 120 complete mitochondrial genome reported showed that the start codon for COI gene evidences an array of diverse designation of COI start codon such as typical ATN, tetranucleotide TTAG and ATAA, newly proposed AAT and AAC and so on. In the case of Lepidoptera, many completely sequenced species showed no typical start codon at the start context of COI and even within the neighboring tRNATyr. In order to clarify, we newly sequenced the beginning context of COI gene, encompassing the neighboring tRNATyr and start region of COI gene from 39 species belonging to eight lepidopteran families. We found the newly sequenced 39 species and 14 available complete lepidopteran mitochondrial genomes all possessed CGA (arginine), which is the first non-overlapping in-frame codon in COI gene. Furthermore, this CGA is highly well aligned in terms of both nucleotide and amin o acid sequences with neighboring region. Thus, the CGA (arginine) may be synapomorphic character for Lepidoptera, functionally constrained. We, therefore, propose the CGA sequence as the start codon for COI gene in lepidopteran insects.