Distribution of two freshwater shrimps, Paratya compressa improvisa (Atyidae) and Palaemon paucidens (Palaemonidae) were studied in 301 sites (lakes and ponds) in Aomori Prefecture, northern Japan in 2017. Paratya c. improvisa and P. paucidens were recorded from 15% and 13 % of the sites surveyed, respectively, and they tended to be found in the sites in desolate areas or those under protections, where invasive alien fishes would not been present. It is suggested that high predation pressure of the introduced largemouth bass Micropterus salmoides has depressed the shrimps considerably in the wide areas of the prefecture since 1990s. A temnocephalidan Scutariella japonica (Scutariellidae) was found on P. c. improvisa from 6 sites in Aomori Prefecture.
Qualitative and quantitative samplings of adult winter stoneflies were conducted in May and/or June 2014, 2015 and 2018 in three snowy valleys at the eastern face of Mt. Tanigawa, northern Gunma Prefecture, central Japan, to reveal faunal composition of stoneflies in snowy valleys which remain until early to late summer. Seven species of winter stoneflies belonging to five genera and three families were collected. Population density of the winter stoneflies ranged from 3.8 to 87.5 individuals per square meter. At least in two valleys, Ichinokurasawa and Yuunosawa, the populations were largely dominated by Apteroperla sp. A8 (Capniidae). Most of the female capniid stoneflies found in May and June had mature eggs. Influence of floods on population density of stoneflies was discussed.
Twenty five species and 8 taxa identified to genera of stoneflies belonging to the families of Chroloperlidae, Taeniopterygidae, Leuctridae and Nemouridae were listed basing upon the Tanida collection deposited in Osaka Museum of Natural History. Mesyatsia imanishii, Nemoura stratum, Paraleuctra ambulanace and Protonemura towadensis were mostly collected on snow from winter to early spring.
I collected six species of wingless winter stoneflies in Gunma Prefecture during April 2011-June 2018. They be-longed to two genera of the family Capniidae, Plecoptera. Among them, Eocapnia nivalis (Uéno, 1929) was the most widely collected both in altitude and horizontally, which was found between 395 m and 1600 m above sea level. In Gunma Prefecture, Eocapnia sp. Ec3 (tentative name) inhabited only in the east foot of Mt. Tanigawa.
Ministry of Land, Infrastructure, Transportation and tourism has conducted a nation-wide census of river environment and organisms (National River Census) since 1990. The census covers riverine plants, benthic invertebrates, terrestrial insects, birds, fishes, and amphibians, reptiles and mammals and planktonic organisms in dam reservoirs. Some members of the authors (K. Tanida and N. Kuhara) have been checked the identification of benthic invertebrates and some aquatic insects. Through the inspection, we found some interesting species in their geographical distribution. Here, we provide the list and records of these species, including Trichoptera: Kisaura hattorii, Polyplectropus malickyi, Arctopsyche spinifera, Hydropsyche dilatata, Macrostemum okinawanum, Lepidostoma kojimai, Apatania kyotoensis, Apatania nikkoensis, Goera kyotonis, Goera nigrosoma, Molanna nervosa, Athripsodes tsudai, Leptocerus moselyi, Triaenodes qinglingensis, Georgium japonicum; Diptera: Deuterophlebia nipponica, and Neohapalothrix kanii.
Quantitative samples of benthic macro-invertebrates were collected from two mountainous streams: Shibukuro Stream (pH 3.1 in average) and Ishiguro Stream (pH 6.7 in average) of Tamagawa River System, Akita Prefecture, northern Honshu from May 15 to November 27, 2017. A total of 83 taxa were identified from Ishiguro Stream, whereas only eight taxa were identified from a highly acidic stream of Shibukuro Stream. The number of taxon increased in spring and autumn at Ishiguro Stream, but it was stable from spring to autumn at Shibukuro Stream. A stonefly shredder, Protonemura kohnoae, and a caddisfly predator, Rhyacophila lezeyi, were dominant in number and biomass at Shibukuro Stream. Larvae of R. lezeyi were often observed to eat nymphs of P. kohnoae at Shibukuro Stream throughout the year.
I investigated distribution of the species belonging to Baetidae in 96 sites in Okayama Prefecture, western Honshu, Japan, from 2010 to 2018. I collected 18 species belonging to 9 genera. I compared collecting rate of baetid nymphs between two types of landform and six types of stream and water, and found that 5 species were frequently collected in mountain area and remaining 13 species in basin and plain area. Among the species which were frequently collected in basin and plain area, nymphs of Acentrella sibirica, Baetiella japonica, Labiobaetis atrebatinus orientalis, Procloeon spp. and Tenuibaetis flexifemora were sometimes collected at sampling sites of headwaters with anthropogenic disturbance. In Takahashigawa, Asahigawa, and Yoshiigawa river systems, I collected more numerous species in these large river systems than in Sasagasegawa river system and small streams in southeastern region of Okayama Prefecture. The factors of the small species number in the latter streams were considered to be low altitude of headwater area, lack of long sections of mountain stream, and human impact.