The giant water bug, Lethocerus deyrolli, is an endangered wetland insect found throughout East Asia. In 2006, the light-attraction flight of L. deyrolli was studied in Gyodong Island, Korea, using artificial light. The flight of L. deyrolli was observed from early June to late October, and two peaks in the numbers of attracted insects were noted in the middle of June and September. L. deyrolli begins to exhibit flight behaviour at a daily mean air temperature of 158C and above, but optimal flight temperatures for the insect are between 178C and 198C, with a wind speed of less than approximately 1.8 m/sec and a relative humidity of around 80%. The length of daylight did not substantially influence the flight pattern. Daily flight occurred principally between 9 pm and 10:30 pm. L. deyrolli individuals attracted by the artificial light were frequently consumed by magpies or house rats. It appears most probable that artificial lights, such as street lights and tennis court lights, constitute a critical factor in the local extinction of L. deyrolli.

We carried out DNA barcoding on 24 Korean tettigonid species of 19 genera deposited in the National Institute of Biological Resources to reevaluate the preliminary identification of each specimen. Sequence divergence of DNA barcodes obtained from 113 samples of the 24 species ranged from 0 to 30.4%, the intraspecific variation was 0–7.3%, and the interspecific divergence was 1.1–30.4%; we could not examine the barcoding gap. In the neighbor‐joining tree, the branch length among individuals of Tettigonia ussuriana, Paratlanticus ussuriensis, and Hexacentrus japonicus were relatively longer than those in other species. The detailed analysis of the morphological characters and DNA barcodes of the above three species revealed that these three species represent species complexes. The T. ussuriana complex comprised T. jungi, T. uvarovi, and T. ussuriana. Paratlanticus ussuriensis cluster contained four species; one cluster was identified as P. palgongensis based on morphological characteristics, but the other three clusters, including the P. ussuriensis cluster, require further detailed taxonomic analysis. Lastly, two species clusters were identified within the Hexacentrus japonicus clade. Based on the 99% sequence similarity obtained by blast search of the NCBI GenBank database, one of the clusters was identified as H. unicolor. Thus, the DNA barcoding revealed the presence of at least three cryptic species in Korean Tettigoniidae, although more detailed taxonomic analyses are required to establish their status. Therefore, we suggest that DNA barcoding is a very useful tool for increasing the identification accuracy of insect collections.