The giant water bug Kirkaldyia deyrolli (Vuillefroy, 1864) is a large aquatic hemiptera endangered in Japan, and collection records are important for estimating the habitat status of this species. Recent genetic analysis suggests that this species may include cryptic species. Thus, the collection of morphological and phylogenetic information is important for reexamining the taxonomy of K. deyrolli.
In this article, we published the collection record information and the specimen depository for one individual of the species collected in Nigata Bay, Kure City, Hiroshima Prefecture in July 2022. Some morphological characteristics are discussed. Additionally, we determined the partial sequences of mitochondrial CO1 in the specimen and conducted molecular phylogenetic analysis. As a result, we determined that the specimen shared characteristics with species populations that were confirmed to inhabit other areas of the Chugoku region by previous studies. Therefore, the individual may have belonged to a surrounding regional population and may have flown to the collection area from elsewhere, so it was not possible to accurately establish the original habitat of the specimen. However, this confirms the record of the giant water bug in Kure City, and until then, the record had been lost in recent years. It gives us hope that populations in the surrounding areas may recover in the future.