Ranatra filiformis group sensu Lansbury, 1972 Diagnosis. Smaller species, body length: males 22–27, females 24–30; siphon moderate to long, ratio of siphon length: body length around 0.7–0.9; vertex in lateral view higher than eye, evenly round, without or with very low tubercle; ratio of eye width: interocular width 0.65–0.98; ratio of anterior pronotal length: posterior pronotal length 1.3–1.7; fore femur slender, flexor side with two teeth nearer to distal end, larger one proximal to smaller one, pre-apical teeth absent; metasternum with posterior margin usually convex (sometimes straight or slightly emarginated); operculum of female at most reaching apex of connexivum. Species included. Ranatra filiformis Fabricius, 1790, R. diminuta Montandon, 1907, R. occidentalis Lansbury, 1972, and R. akoitachta Nieser, 1996. Note. For comparison between species of this group, see Lansbury (1972) and Nieser (1996).

Published as part of Tran, A. D. & Zettel, H., 2021, Taxonomic review of the Ranatra gracilis group sensu Lansbury, 1972 (Nepomorpha: Nepidae), with descriptions of four new species, pp. 45-70 in Raffles Bulletin of Zoology 69 on page 48, DOI: 10.26107/RBZ-2021-0005, http://zenodo.org/record/5351678