We investigated the seasonal occurrences, reproductive seasons, and habitat environments of an endangered damselfly Paracercion plagiosum (Odonata: Coenagrionidae) in ponds neighboring Lake Izunuma–Uchinuma of the northern Miyagi Prefecture, Japan. P. plagiosum was observed from early June to mid-August in both ponds, with the peak of the adults observed in late June. Reproductive behavior (tandem linkage, mating, and egg-laying) was observed from late June to early August in both ponds, and the aquatic plant composition differed between the two ponds. Several species of emerged plants were observed at the water edge, and the floating-leaved plants Trapa spp. were observed on the water surface. However, the free-floating plant Utricularia australis was observed only in one of the targeted ponds. In the Pond A dominated by Trapa spp., all egg-laying of this species occurred in Trapa spp., but in the Pond B where Trapa spp. and U. australis coexisted, 70％ of egg-laying occurred in U. australis. This suggests that egg-laying on the U. australis may be a factor that increases the fitness of this species compared to Trapa spp. In Lake Izunuma–Uchinuma, Nelumbo nucifera and Trapa spp. have become dominant over a wide area of the lake due to eutrophication, and the environment in which U. australis grows has become precious. Environmental management of the ponds and restoration activity of lakeshore vegetation zone in Lake Izunuma–Uchinuma will be important for the conservation of this endangered species.

Stenichneumon Thomson, 1893 comprises 23 species in the Holarctic, Oriental, and Neotropical regions. In Japan, five species, S. culpator iwatensis Uchida, 1926, S. militarius naironis Uchida, 1926, S. nigriorbitalis Uchida, 1930, S. odaiensis Uchida, 1932 and S. posticalis (Matsumura, 1912) have been recorded. Here, we report new host records, S. culpator iwatensis emerged from pupa of Autographa nigrisigna (Walker, 1858) and S. posticalis emerged from pupa of Ctenoplusia agnata (Staudinger, 1892). The latter host was collected as larva, and this is the first information on the host life stage attacked by this genus. New distributional records are S. nigriorbitalis from Shikoku and S. odaiensis from Hokkaido. In addition, we provided an identification key to Japanese species of the genus.

Graphium cloanthus (Westwood, 1841) had been known for four subspecies: ssp. cloanthus (Westwood, 1841), ssp. clymenus (Leech, 1893), ssp. kuge (Fruhstorfer, 1908) and ssp. sumatranum (Hagen, 1894). Among them, ssp. sumatranum was raised to specific level as an independent species, G. sumatranum (Hagen, 1894). In the wing markings, coloration of spots of G. sumatranum is yellower than those of G. cloanthus. In this report, the male genitalia of the two species were morphologically compared and the anellifer, harpe and ampulla of the valva were found to be stably different between them.