Common Backswimmer - Notonecta glauca


    Up to nearly 2 cm in size, and commonly called backswimmers because they swim upside down and are often seen at the surface of the water. Notonecta glauca is light brown in colour with a number of dark markings and large reddish eyes. It often looks silvery as air becomes trapped in a layer of bristles covering the lower surface. The powerful oar-like hind legs are modified for swimming; they are long, flattened and fringed with hairs

    Similar Species

    There are four UK Notonecta species and whilst they look broadly similar they can all be separated in the field from the different elytral markings. See ID Aids below.

    N. glauca is most likely to be confused with N. viridis. Both have pale wing coverings (these are darker in the other two species). The front corners of the N. viridis pronotum are pointed and they extend partly under the eye. The front pronotum corners are more or less square in N. glauca.

    Identification difficulty
    Identification aids


    Recording advice

    A good photo of the dorsal surface is needed and ideally a side view showing the front corner of the pronotum. Alternatively the specimen needs to have been examined and the ID method described.


    Water dwelling, in ponds, cattle troughs, etc.

    When to see it

    All year round.

    Life History

    Backswimmers are predators that attack prey as large as tadpoles and small fish, the forelegs, which are short and strong, are used for grabbing prey. In contrast to other aquatic insects that cling to submerged objects using the extra oxygen supply from haemoglobin in their abdomen, instead of using oxygen dissolved in the water.

    UK Status

    Common: the most widespread and abundant of the genus in Britain.

    VC55 Status

    Very common in Leicestershire and Rutland.

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    Leicestershire & Rutland Map

    MAP KEY:

    Yellow squares = NBN records (all known data)
    Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

    UK Map