Culex (Eumelanomyia) hayashii Yamada

Harbach, Ralph E. & Wilkerson, Richard C., 2023, The insupportable validity of mosquito subspecies (Diptera: Culicidae) and their exclusion from culicid classification, Zootaxa 5303 (1), pp. 1-184 : 96

Culex (Eumelanomyia) hayashii Yamada

subspecies hayashii Yamada, 1917 —original combination: Culex hayashii . Distribution: Japan, People’s Republic of China, Russia, South Korea, Taiwan ( Wilkerson et al. 2021).

subspecies ryukyuanus Tanaka, Mizusawa & Saugstad, 1979 —original combination: Culex (Eumelanomyia) hayashii ryukyuanus . Distribution: Japan (Ryukyu Archipelago) ( Tanaka et al. 1979).

Sirivanakarn (1972), in his revisionary study of the subgenus Eumelanomyia in Southeast Asia and adjacent areas, stated that “The adults of C. hayashii show a great deal of variation in size, color, texture of scutal scales and in the length of male palpus. The specimens from the Ryukyu Islands differ from the specimens from Japan and Korea in smaller size, darker coloration, finer scutal scales and shorter male pulpus [sic]. However, these differences are not correlated with any differentiation in the male terminalia [genitalia], indicating that there is in all probability only one species involved.” Tanaka et al. (1979) interpreted ryukyuanus to be a subspecies distinct from the type form based on the following characteristics: Generally smaller body size, wing with a smaller ratio of the length of cell R 2 to the length of vein R 2+3, a slight difference in the ratio of the length of hindtarsomere 1 to the length of the hindtibia (0.98–1.11 as opposed to 0.85–1.03 in the type form), male with shorter maxillary palpus (palpomere 2 shorter than it is in the type form). They stated that the larva of ryukyuanus did not appear to be significantly different from hayashii sensu stricto on Japan’s main island (Honshu).

The Ryukyu Archipelago comprises an arc of 55 islands and islets that extend about 1,000 km southwestward from 40 km south of Kyushu, the southernmost of Japan’s main islands, to 100 km east of northern Taiwan. The chain of islands is divided by two large gaps, a northern gap of about 270 km between Yakushima Island and the Amami island group, and a southern gap of about 280 km between the islands of Okinawa and Miyako. The flora and fauna tend to be very different on either side of these gaps, and forms that occur on islands of the Archipelago that have been regarded as subspecies are proving to be genetically distinct ( Toma et al. 2019; Somboon et al. 2020a; Wilkerson et al. 2022). For example, Toma et al. (2019) clearly showed that Tripteroides bambusa yaeyamensis Tanaka, Mizusawa & Saugstad, 1979 in the central and southern regions of the archipelago is molecularly and genetically distinct from Tp. bambusa ( Yamada, 1917) in the northern Palaearctic region of Japan. Based on the results of their study and similar findings regarding the specific status of Aedes (Hulecoeteomyia) yaeyamensis Tanaka, Mizusawa & Saugstad, 1979 ( Somboon et al. 2020a; Wilkerson et al. 2022), despite the morphological similarity observed by Sirivanakarn (1972) and Tanaka et al. (1979), we believe it is likely molecular study will reveal that ryukyuanus and hayashii sensu stricto are separate species. Therefore, unless genetic evidence proves otherwise, we hereby formally elevate ryukyuanus to specific rank: Culex (Eumelanomyia) ryukyuanus Tanaka, Mizusawa & Saugstad, 1979 . Culex ryukyuanus is currently listed as a species in the Encyclopedia of Life.

For comparison, see the analogous treatments of the subspecies of Toxorhynchites manicatus ( Edwards, 1921a) and Uranotaenia novobscura Barraud, 1934 presented below.