Australian Biological Resources Study

Australian Faunal Directory


Regional Maps


Compiler and date details

October 2010 - Dr G. Cassis, University of New South Wales, Sydney, New South Wales


The Pleidae, or pygmy backswimmers, are a family of truly aquatic, nepomorphan bugs, comprising three genera and 38 species (Slater 1982; Zoological Record 1980–1994; Henry 2009; Polhemus, J.T. pers. comm.). They are cosmopolitan and are most diverse in the tropics.

Pleids are very small, ranging in length from 2 to 3 mm. They are coleopteriform, ovoid, strongly convex and tapered caudally. They are generally pale in colour. The head is hypognathous. The eyes are large and ocelli are absent. The antennae are 3-segmented and not visible from above. The labium is 4-segmented and awl-shaped. The pronotum is large, quadrate, and either punctate or reticulate. The scutellum is triangular. The forewings are uniform, without a differentiated membrane, and fit closely over the abdomen. The hind wings are often shortened. The larvae have dorsal abdominal glands between terga III and IV. The metathoracic glands are sac-like and have a single midventral opening (Aldrich 1988). The coxae are open and pagiopodous. The hind legs are characterised by long hairs adapted for swimming. The tarsi are 3-segmented and the hind pretarsus has two claws (Slater 1982).

Pleids are predaceous and feed on mosquito larvae and other invertebrates, such as ostracods and Daphnia Müller species (Polhemus 1988). Pleids are usually found in quiet waters. Like notonectids, pleids swim upside down in a rowing manner. Carver et al. (1991) report that they are poor swimmers, preferring to walk on or through thick submerged vegetation. Australian pleids are most common in swamps and lakes.

Esaki & China (1927) first recognised pleids as a family and allied them with the Helotrephidae. Schuh (1986) and Carver et al. (1991) placed them in the Notonectoidea, which is followed in the Catalogue. Alternatively, Štys & Jansson (1988) placed the Pleidae, together with Helotrephidae, in the superfamily Pleoidea. Rieger (1976), in his phylogenetic analysis of the Nepomorpha, considered the Pleidae and Helotrephidae to be the most apomorphic nepomorphans. Lundblad (1933) reviewed the Pleidae and described one new Australian species. Drake & Chapman (1953) gave an account of the Western Hemisphere species and Polhemus (1984) updated the North American fauna, cataloguing it in a subsequent work (Polhemus 1988).

Carver et al. (1991) listed Australian pleids as belonging to the genus Plea. Štys & Jansson (1988), however, listed this genus as restricted to the Palaearctic Region. In Cassis & Gross (1995) the three species that occur in Australia are referred to Paraplea Esaki & China. P. brunni (Kirkaldy) is widely distributed in Australia, P. halei (Lundblad) is a temperate species known from Victoria and Tasmania, and P. liturata (Fieber) is a tropical species known from the Northern Territory, Java and New Caledonia. Andersen & Weir (2004b) provided a key for the Australian pleids.


General References

Aldrich, J.R. 1988. Chemical ecology of the Heteroptera. Annual Review of Entomology 33: 211-238

Andersen, N.M. & Weir, T.A. 2004. Australian Water Bugs. Their Biology and Identification (Hemiptera-Heteroptera, Gerromorpha & Nepomorpha). Entomonographen Denmark : Apollo Books Vol. 14 344 pp.

Carver, M., Gross, G.F. & Woodward, T.E. 1991. Hemiptera (bugs, leafhoppers, cicadas, aphids, scale insects, etc.) [with contributions by Cassis, G., Evans, J.W., Fletcher, M.J., Hill, L., Lansbury, I., Malipatil, M.B., Monteith, G.B., Moulds, M.S., Polhemus, J.T., Slater, J.A., Štys, P., Taylor, K.L., Weir, T.A. & Williams, D.J.]. pp. 429-509 in CSIRO (ed.). The Insects of Australia. A textbook for students and research workers. Melbourne : Melbourne University Press Vol. 1 xiii 542 pp.

Cassis, G. & Gross, G.F. 1995. Hemiptera: Heteroptera (Coleorrhuncha to Cimicomorpha). pp. 1-501 in Houston, W.W.K. & Maynard, G.V. (eds). Zoological Catalogue of Australia. Hemiptera: Coleorrhyncha to Cimicomorpha. Melbourne : CSIRO Australia Vol. 27.3A xv 506 pp.

Drake, C.J. & Chapman, H.C. 1953. Preliminary report on the Pleidae (Hemiptera) of the Americas. Proceedings of the Biological Society of Washington 66: 53-59

Esaki, T. & China, W.E. 1927. A new family of aquatic Heteroptera. Transactions of the Entomological Society of London 75: 279-295

Lundblad, O. 1933. Zur Kenntnis der aquatilen und semiaquatilen Hemipteren von Sumatra, Java und Bali auf Grund des Materials der Deutschen Limnologischen Sunda-Expedition, nebst Revision einiger anderer, indoaustralischer Arten. Archiv für Hydrobiologie 12: 1-195, 263-489

Polhemus, D.A. 1988. Family Pleidae Fieber, 1851: the pygmy backswimmers. pp. 608-612 in Henry, T.J. & Froeschner, R.C. (eds). Catalog of the Heteroptera, or True Bugs, of Canada and the Continental United States. Leiden : E.J. Brill xix 958 pp.

Polhemus, J.T. 1984. Aquatic and semiaquatic Hemiptera. pp. 231-260 in Merrit, R.W. & Cummins, K.W. (eds). An Introduction to the Aquatic Insects of North America. Dubuque : Kendall-Hunt.

Rieger, C. 1976. Skelett und Muskulatur des Kopfes und Prothorax von Ochterus marginatus Latreille. Beitrag zur Klärung der phylogenetischen der Ochteridae (Insecta, Heteroptera). Zoomorphology (Berlin) 83: 109-191

Schuh, R.T. 1986. The influence of cladistics on Heteropteran classification. Annual Review of Entomology 31: 67-93

Slater, J.A. 1982. Hemiptera. pp. 417-447 in Parker, S.P. (ed.). Synopsis and Classification of Living Organisms. New York : McGraw Hill Book Co.

Štys, P. & Jansson, A. 1988. Check-list of recent family-group and genus-group names of Nepomorpha (Heteroptera) of the world. Acta Entomologica Fennica 50: 1-44


History of changes

Note that this list may be incomplete for dates prior to September 2013.
Published As part of group Action Date Action Type Compiler(s)
30-Nov-2012 30-Nov-2012 MODIFIED
15-Aug-2012 15-Aug-2012 MODIFIED
20-Oct-2010 20-Oct-2010 MODIFIED
12-Feb-2010 (import)