Water environments and benthic invertebrate fauna were studied in a spring-fed Gudari-numa Stream in Hakkoda Mountains, Aomori Prefecture, northern Japan during 2014–2019. The stream has ever-cool and less organic overlying water and productive bottoms with abundant attached algae. A total of more than 129 species of benthic invertebrates belonging to eleven phyla were recorded from the stream. Along with epigean forms, the benthic fauna contained rich stygobites such as Pseudocrangonyx amphipods, nerillid and lumbriculid annelids along with stygophile forms in the shallow hyporheic zone. The zoobenthic assemblages entirely lacked several groups of animals which are common in neighboring streams, for example, odonates, heptageniids and net-spinning trichopterans, while the community had rich and abundant diamesine and orthocladiine chironomids, and planariid flatworms. The lopsided structure of the zoobenthic community could be related with the strongly localized organic matters to the bottoms as well as ever cool and stable enviroments.

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In 2018–2019, life histories of two caddisfly species of the genus Brachycentrus Curtis, B. americanus (Banks, 1899) and B. kuwayamai Wiggins et al., 1985, were studied in Moizari-gawa Creek, Eniwa City (42.8851N, 141.5596E, 35 m above sea level), and in Abira-gawa Creek, Abira Town (42.8746N, 141.9098E, 120 m), respectively, on Hokkaido. Five instars of larvae were detected by head width distribution in both species. Brachycentrus americanus was univoltine with a long adult flight period from mid May–early November. Two larval cohorts were detected in the population, with first instar larvae appearing twice, in July and December. Subsequently, two peaks in the frequency distribution of instars appeared in many months. In contrast, though B. kuwayamai was also univoltine, it had a short adult flight period from late May to mid June, and displayed a narrow range of larval instars in almost all months. In B. kuwayamai, many slender plant pieces (often more than 30 pieces) were attached to about 80% of fourth instar and 95% of fifth instar larval cases. Less than 1% of third to fifth instar B. americanus larvae added 1–4 short plant pieces to their cases. Dominant gut contents of final instar B. americanus larvae were aquatic plant fragments (about 50%) and terrestrial plant fragments (about 30%), and for B. kuwayamai they were amorphous detritus (about 50%) and terrestrial plant fragments (about 25%). The larval frequency feeding on animals increased according to larval development to about 50% in final instar larvae of both species.

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Mayflies (Insecta: Ephemeroptera) were investigated from 2010 to 2019 in Okayama Prefecture, western Honshu, Japan. I collected 80 mayfly species belonging to 12 families. Ten species were recorded for the first time in Okayama Prefecture. 13 species were only narrowed down to family or genus, and 3 species were considered to comprise plural species. I provided a number as provisional name to the remaining 10 species. Among 69 species ever recorded in Okayama Prefecture, 10 species were not collected in this study. Number of mayfly species in Okayama Prefecture increased to 90, and an inventory of these species was compiled. Discussion was presented with regard to species composition in Okayama Prefecture and comparison of the inventory with other prefectures in central and western area of Honshu island.

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Field studies of the winter stoneflies (Plecoptera) of Nurigawa River in Gunma Prefecture, cental Japan, from November 2019 to April 2020, resulted in a total 17 species (16 named species and 1 undetermined species) belonging to 9 genera of 4 families. Of the 17 species, Eocapnia shigensis is the most abundant of all species, and this has not been confirmed in other water systems in Gunma Prefecture, except Kinonezawa Stream. Eucapnopsis quattuorsegmentata was confirmed for the first time in Gunma Prefecture.

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The genus and species Cercobrachys minutus (Tshernova, 1952) in the family Caenidae is recorded for the first time in Japan. Eggs of this species are redescribed. Diagnoses, illustrations of nymphs and keys to species are provided.

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The mayfly species, Ephoron shigae (Takahashi), family Polymitarcyidae is recorded for the first time in Shiga Prefecture. Photographs and notes are provided.

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