Japanese Journal of Systematic Entomology, 26 (2): 191–200. December 30, 2020. REVIEW ARTICLE Species Diversity of Aquatic Hemiptera and Coleoptera in Japan Masakazu HAYASHI1), Jun NAKAJIMA2), Kazuo ISHIDA3), Tadashi KITANO4), Hiroyuki YOSHITOMI5) 1) Hoshizaki Green Foundation, Sono, Izumo, 691-0076 Japan 2) Fukuoka Institute of Health and Environmental Sciences, Fukuoka, 818-0135 Japan 3) Narashino, Chiba, 275-0012 Japan 4) Department of Human Development, School of Humanities and Culture, Tokai University, Hiratsuka, 259-1292 Japan 5) Ehime University Museum, Matsuyama, 790-8577 Japan Abstract The species diversity of aquatic Hemiptera and Coleoptera in Japan on the water surface and in the water column during both larval and adult stages was reviewed. The list was based on the latest taxonomic knowledge, and summarized species recorded in Japan at the end of 2019. Hemiptera included 118 species in 13 families, among which 22 species (18.6%) were endemic to Japan. Coleoptera included 358 species in 12 families, among which 156 species (43.6%) were endemic to Japan. A total of 29 taxa of Hemiptera and 109 taxa of Coleoptera listed in the Red List of Japan were published in 2019. The total number of Coleoptera taxa increased from 41 to 109 from 2007 to 2019. Keywords: aquatic beetles, aquatic true bugs, biodiversity of Japan Introduction the water surface and in the water column during both their larval and adult stages. In Coleoptera, these are defined as The Japanese archipelago is located in the ranges of “true water beetles” (Jäch, 1998); however, there is a similarly latitude 20–46° N and longitude 122–153° E, and contains definable species in Hemiptera. The authors published a 6852 large and small islands on the east side of Eurasia bibliographical picture book summarizing these Japanese (Geospatial Information Authority of Japan, 2020). The Kuril species (Nakajima et al., 2020). During the preparation Islands, the four main islands (Hokkaido, Honshu, Shikoku, of this book, the current situation of Japanese species was and Kyushu), and the Ryukyu Islands form island arcs. reexamined. No data have been compiled on species diversity Geologically, the archipelago is dominated by continental to date; therefore, the number of known species, endemic taxa, islands formed by the separation of the continental crust into endangered species, and genetic diversity studies are discussed the Pacific Ocean during the Miocene (Otofuji & Mastuda, in the present review. In particular, the increase in endangered 1987; Barnes, 2003). The island arcs are in the subduction species of aquatic Coleoptera is a significant problem. zone of the oceanic plate, and crustal deformation is active. The main island has mountain ranges that are 2,000–3,000 Methods m above sea level and contain several volcanic fronts. In the North Pacific Ocean, the Daito, Ryukyu, and Ogasawara The species list (Nakajima et al., 2020) is mainly based on Islands are oceanic islands. Kawai & Tanida (2018) and incorporates the latest taxonomic The climate of Japan is warm and humid. From the knowledge and summarizes species recorded in Japan at Japan Meteorological Agency (2020) statistics, the average the end of 2019 (Kamite & Hayashi, 2019; Minoshima & temperature and precipitation values for the 30 years from Inahata, 2019; Nakajima, 2020). Counting was performed 1981 to 2010 were 15.4 °C and 1528.8 mm in Tokyo, and 8.9 at the species level, and taxa that were divided into multiple °C and 1106.5 mm in Sapporo, Hokkaido, respectively. The subspecies were grouped into species. average annual temperature in Naha in Okinawa Prefecture is Endangered species are based on the Red List 2019 23.8 °C, and the annual precipitation is 2099.3 mm. Surface published by the Ministry of the Environment, Japan (MOE, water is abundant due to high precipitation. Paddy fields are 2019a). The list is based on species and subspecies ranks, and mainly used as farmlands in the plains, and valleys in low does not represent the exact number of species. mountainous areas are often used as paddy fields because rice The distribution was divided into seven regions (Fig. 1): is the primary agricultural crop. Many agricultural reservoirs Hokkaido, Honshu, Shikoku, Kyushu, Nansei Islands (Ryukyu are created in areas with relatively low precipitation, and there Islands), Tsushima, and Ogasawara Islands. Of these, the are approximately 96,000 locations nationwide (Ministry of three major islands of Honshu, Shikoku, and Kyushu are often Agriculture, Forestry and Fisheries, 2020). Therefore, both lotic classified as an integrated area in terms of biogeography (e.g., and lentic water environments are abundant in Japan. In the mid- Millien-Parra & Jaeger, 1999). latitudes of the Northern Hemisphere, surface water-rich areas Non-native species were not included in the species count, are limited. Owing to the abundance of surface water, a variety which was only applicable to Rhagadotarsus kraepelini of aquatic insects adapt to various inland water environments. Breddin, 1905 (Hemiptera: Gerridae). This review covered species of aquatic insects that live on Ⓒ Japanese Society of Systematic Entomology 192 Hayashi, M., J. Nakajima, K. Ishida, T. Kitano and H. Yoshitomi 400 45° 350 300 Hokkaido 40° 250 Coleoptera 200 35° 150 Tsushima Honshu 100 Hemiptera Shikoku 50 30° Kyushu 0 Nansei Isls Ogasawara Isls 1750 1800 1850 1900 1950 2000 Fig. 2. Cumulative number of described species and subspecies by 25°N 0 250 500 year. Only valid names are counted. Km 125°E 130° 135° 140° 145° Fig. 1. Biogeographical division in this study. Hemiptera Coleoptera Sharp , 64 Miyamoto, 21 Others, 163 M.Satô , 36 Others, 59 Esaki, 15 Nomura , 31 Matsumura, 12 Jäch , 28 Horváth, 10 Nakane , 21 Clark, 10 Regimbart, 11 Díaz , 17 Fig. 3. Number of described species/ S.Uéno , 11 Scott, 5 Kamite , 15 subspecies per author. Only valid Fieber, 5 Fabricius, 6 Matsui , 11 Kamiya , 11 Fabricius , 12 names are counted. Habitat of aquatic species the families Nepidae, Belostomatidae, Corixidae, Naucoridae, Aphelocheiridae, Notonectidae, Pleidae, Helotrephidae, Nakajima et al. (2020) classified the habitat of aquatic Mesoveliidae, Hydrometridae, Veliidae, Gerridae, and insects into ponds, rivers, puddles, paddy fields, wet rocks, Hermatobatidae. The families of other groups are semi- sea, and groundwater. aquatic, for example, Hebridae, Saldidae, and Ochteridae. Ponds include natural waters such as ponds, lakes, marshes, and agricultural reservoirs. Taxonomic history Rivers include running water environments such as rivers The first species of aquatic Hemiptera described in Japan and streams. was Appasus japonicus Vuillefroy, 1864. Then, Ilyocoris Puddles are temporary small water bodies or very small cimicoides exclamationis (Scott, 1874), Hydrometra water bodies recharged by springs. albolineata (Scott, 1874), Laccotrephes japonensis Scott, Paddy fields are farmland where rice is grown; dry rice 1874, Ranatra unicolor Scott, 1874, and Microvelia douglasi fields are dry from autumn to winter, and wet rice fields are Scott, 1874 were described as Japanese species of Hemiptera damp all year. by Scott (1874). Wet rocks, also known as hygropetric environments, are According to Hayashi & Miyamoto (2018), the study environments in which the surface of the rocks is constantly of Hemiptera was begun by a Japanese taxonomist after moist due to currents and splashes flowing through the rock. 1900. Shônen Matsumura described Aphelocheirus vittatus Sea includes intertidal zones such as tidal flats and rocky Matsumura, 1905, Anisops ogasawarensis Matsumura, 1915, reefs, inner bays, and coastal waters. and 10 other species (Matsumura, 1905, 1915). During the Groundwater is a water environment that exists in 1950s and 1960s, 21 species were described by Teiso Esaki and underground gravel deposits and fractured zones. Syôiti Miyamoto (Esaki & Miyamoto, 1955; Miyamoto, 1958). While the valid species and subspecies were accrued each Hemiptera year, the increase was remarkable during the 1950s–1960s The taxa of Japanese species that inhabit the water surface (Fig. 2), which was due to the research undertaken by Esaki and water column during their larval and adult stages include and Miyamoto. However, since the 1980s, the increase in the December 30, 2020, JJSE 26 (2) Review: Species Diversity of Aquatic Hemiptera and Coleoptera in Japan 193 Fig. 4. Known species number for each family of aquatic Hemiptera. Table 1. Species number for each area of aquatic Hemiptera, and endemic species number in parentheses. HSK shows major three islands, Honshu, Shikoku and Kyushu. Family Japan Hokkaido Honshu Shikoku Kyushu Nansei Isles Tsushima Ogasawara Isles HSK Nepidae 7(0) 2(0) 4(0) 4(0) 3(0) 6(0) 2(0) 0(0) 4(0) Belostomatidae 5(0) 3(0) 3(0) 3(0) 3(0) 3(0) 2(0) 0(0) 3(0) Corixidae 29(3) 10(1) 20(0) 15(0) 17(0) 11(1) 4(0) 0(0) 21(0) Naucoridae 1(0) 0(0) 1(0) 0(0) 1(0) 0(0) 0(0) 0(0) 1(0) Aphelocheiridae 3(1) 0(0) 3(1) 1(0) 2(0) 0(0) 0(0) 0(0) 3(1) Notonectidae 11(0) 2(0) 4(0) 3(0) 4(0) 9(0) 2(0) 1(0) 5(0) Pleidae 3(0) 0(0) 2(0) 2(0) 2(0) 2(0) 1(0) 0(0) 2(0) Helotrephidae 1(1) 0(0) 0(0) 0(0) 0(0) 1(1) 0(0) 0(0) 0(0) Mesoveliidae 6(1) 4(0) 6(0) 5(0) 4(0) 3(0) 1(0) 1(0) 6(0) Hydrometridae 5(0) 2(0) 4(0) 3(0) 3(0) 3(0) 3(0) 0(0) 4(0) Veliidae 19(12) 2(0) 9(1) 7(0) 8(0) 15(7) 6(0) 2(1) 9(1) Gerridae 27(3) 11(0) 16(0) 10(0) 14(1) 13(0) 9(0) 1(1) 17(1) Hermatobatidae 1(1) 0(0) 0(0) 0(0) 0(0) 1(1) 0(0) 0(0) 0(0) Total 118(22) 36(1) 72(2) 53(0) 61(1) 67(10) 30(0) 5(2) 75(3) number of species described has not occurred, yet the number of Gerridae, 19 species of Veliidae, and 11 species of of species in Japan has increased.