Belongs within: Panheteroptera.
The Notonectoidea, backswimmers, are a group of aquatic, predatory bugs with a strongly, transversely arched body and a short or absent forewing membrane. In members of the family Notonectidae, the hind legs are oar-like with a single terminal claw and flattened tibiae bearing a fringe of long hairs (Carver et al. 1991). This hair fringe is absent in the small species of the families Pleidae and Helotrephidae. Pleidae have a punctate or reticulate pattern on the pronotum and a vestigial or absent hemelytral membrane (Carver et al. 1991). Helotrephidae have the head and thorax fused, a large scutellum, and one- or two-segmented antennae (Richards & Davies 1977).
Characters (from Richards & Davies 1977): Aquatic species; rostrum more or less elongate, three- or four-segmented; antennae always concealed; fore tarsi not spatulate; ocelli absent.
<==NotonectoideaCGW91
| i. s.: MesotrephesS02 [MesotrephidaeSP02]
|--+--HelotrephidaeGE05
| `--Pleidae [Pleinae]GE05
| |--PleaCGW91
| | |--P. atomariaRD77
| | |--P. leachi [incl. P. minutissima]H01
| | `--P. rufonotata Distant 1914D14
| `--ParapleaPH10
`--NotonectidaeGE05
| i. s.: NepidiumGE05
| AsionectaGE05
| NotonectitesGE05
| PelonectaGE05
| Buenoa scimitraWL09
| Ploa minutissima (Linnaeus 1758)L49, L58 [=Notonecta minutissimaL49]
|--ClypostemmatinaeS02
| |--Canteronecta irajaeS02
| `--ClypostemmaGE05
| |--C. limnaS02
| `--C. xyphiale Popov 1964ZG05
|--NotonectinaeCGW91
| |--Nychia sapphoCGW91
| |--EnitharesCGW91
| | |--E. bergrothi Montand. 1892D14
| | `--E. woodwardiCGW91
| `--Notonecta Linnaeus 1758L58
| |--N. glauca Linnaeus 1758L58 [incl. No. furcataL49, No. marmoreaL49, Nepa notonectaL49]
| |--N. handlirschiCGW91
| |--N. maculataRD77
| |--N. melanotaR26
| |--N. montandoni Kirkaldy 1897I92
| |--N. sieblosiensisS02
| |--N. triguttataI92
| `--N. variegataR26
`--AnisopinaeCGW91
|--Paranisops inconstansCGW91
|--WalambianisopsCGW91
`--AnisopsCGW91
|--A. assimilisD14
|--A. calcaratusTDC06
|--A. canaliculatusPH10
|--A. cleopatra Distant 1914D14
|--A. deichmuelleriS02
|--A. elstoniPH10
|--A. gratusTDC06
|--A. hackeriPH10
|--A. heydeniS02
|--A. hyperion Kirk 1898D14
|--A. inconstansWEE70
|--A. nabillusPH10
|--A. nasutaPH10
|--A. niveus [=Notonecta nivea]L49
|--A. occipitalisPH10
|--A. paraexigerusPH10
|--A. stali Kirkaldy 1904T13
|--A. thienemanniTDC06
`--A. wakefieldiPC66
*Type species of generic name indicated
References
[CGW91] Carver, M., G. F. Gross & T. E. Woodward. 1991. Hemiptera (bugs, leafhoppers, cicadas, aphids, scale insects etc.) In: CSIRO. The Insects of Australia: A textbook for students and research workers 2nd ed. vol. 1 pp. 429–509. Melbourne University Press: Carlton (Victoria).
[D14] Distant, W. L. 1914. Rhynchota from New Caledonia and the surrounding islands. In: Sarasin, F., & J. Roux (eds) Nova Caledonia: Forschungen in Neu-Caledonian und auf den Loyalty-Inseln. A. Zoologie vol. 1 pt 4 pp. 369–390, pls 11–12. C. W. Kreidels Verlag: Wiesbaden.
[GE05] Grimaldi, D., & M. S. Engel. 2005. Evolution of the Insects. Cambridge University Press: New York.
[H01] Horváth, G. 1901. Hemipterák [Hemiptera]. In: Horváth, G. (ed.) Zichy Jenő Gróf Harmadik Ázsiai Utazása [Dritte Asiatische Forschungsreise des Grafen Eugen Zichy] vol. 2. Zichy Jenő Gróf Harmadik Ázsiai Utazásának Állattani Eredményei [Zoologische Ergebnisse der Dritten Asiatischen Forschungsreise des Grafen Eugen Zichy] pp. 245–274. Victor Hornyánszky: Budapest, and Karl W. Hierseman: Leipzig.
[I92] Iwahashi, J. (ed.) 1992. Reddo Deeta Animaruzu: a pictorial of Japanese fauna facing extinction. JICC: Tokyo.
[L58] Linnaeus, C. 1758. Systema Naturae per Regna Tria Naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis revised 10th ed. vol. 1. Laurentii Salvii: Holmiae.
[L49] Lucas, H. 1849. Exploration Scientifique de l’Algérie pendant les années 1840, 1841, 1842 publiée par ordre du gouvernement et avec le concours d’une commission académique. Sciences physiques. Zoologie. II. Histoire naturelle des animaux articulés. Troisième partie. Insectes (suite). Imprimerie Nationale: Paris.
[PC66] Pendergrast, J. G., & D. R. Cowley. 1966. An Introduction to New Zealand Freshwater Insects. Collins: Auckland.
[PH10] Pinder, A. M., S. A. Halse, R. J. Shiel & J. M. McRae. 2010. An arid zone awash with diversity: patterns in the distribution of aquatic invertebrates in the Pilbara region of Western Australia. Records of the Western Australian Museum Supplement 78 (1): 205–246.
[RD77] Richards, O. W., & R. G. Davies. 1977. Imms’ General Textbook of Entomology 10th ed. vol. 2. Classification and Biology. Chapman and Hall: London.
[R26] Risso, A. 1826. Histoire naturelle des principales productions de l’Europe méridionale et particulièrement de celles des environs de Nice et des Alpes maritimes vol. 5. F.-G. Levrault: Paris.
[SP02] Shcherbakov, D. E., & Yu. A. Popov. 2002. Superorder Cimicidea Laicharting, 1781: Order Hemiptera Linné, 1758. The bugs, cicadas, plantlice, scale insects, etc. [=Cimicida Laicharting, 1781, =Homoptera Leach, 1815+Heteroptera Latreille, 1810). In: Rasnitsyn, A. P., & D. L. J. Quicke (eds) History of Insects pp. 143–157. Kluwer Academic Publishers: Dordrecht.
[S02] Sinitshenkova, N. D. 2002. Ecological history of the aquatic insects. In: Rasnitsyn, A. P., & D. L. J. Quicke (eds) History of Insects pp. 388–426. Kluwer Academic Publishers: Dordrecht.
[T13] Taylor, C. K. 2013. Annotated bibliography for Barrow Island terrestrial invertebrates. Records of the Western Australian Museum Supplement 83: 135–144.
[TDC06] Timms, B. V., B. Datson & M. Coleman. 2006. The wetlands of the Lake Carey catchment, northeast Goldfields of Western Australia, with special reference to large branchiopods. Journal of the Royal Society of Western Australia 89 (4): 175–183.
[WL09] Walter, D. E., E. E. Lindquist, I. M. Smith, D. R. Cook & G. W. Krantz. 2009. Order Trombidiformes. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 233–420. Texas Tech University Press.
[WEE70] Woodward, T. E., J. W. Evans & V. F. Eastop. 1970. Hemiptera (bugs, leafhoppers, etc.) In: CSIRO. The Insects of Australia: A textbook for students and research workers pp. 387–457. Melbourne University Press.
[ZG05] Zhang, J., V. B. Golub, Y. A. Popov & D. E. Shcherbakov. 2005. Ignotingidae fam. nov. (Insecta: Heteroptera: Tingoidea), the earliest lace bugs from the Upper Mesozoic of eastern China. Cretaceous Research 26: 783–792.