Insects of Britain and Ireland: the families of Hemiptera

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L. Watson and M. J. Dallwitz


Backswimmers, Boatflies, Water Boatmen.

Salient features of adults. Foraging under water.

Predacious (on arthropods, tadpoles and small fish). Large; (11–)15(–17) mm long; fliers; swimming and moving under water on their backs; relatively stout bodied. Rostrum clearly separated ventrally from the prosternum by a sclerotized gula; 4 segmented. Antennae inserted underneath the head and much shorter than it, generally invisible from above; 4 segmented; non-aristate. Ocelli absent. Fore-wings well developed; in the resting insect sloping roof-like over the abdomen (in association with the dorsally keeled form of the back-swimming insect); differentiated into a basally thickened and a distally membranous region; with a clavus. Fore-legs non-raptorial (although they are used to grasp the prey). Tarsi 2 segmented.

Abdomen with a ventral furrow containing a broad median keel; the fore- and mid-legs similar in form and unmodified, the hind tibiae flattened and hair-fringed, constituting oars. Air is carried under water in a bubble, which is trapped by rows of hydrofuge hairs on the underside of the body and which extends to fill the space between the hemelytra and the back of the abdomen.

Taxonomy. Suborder Heteroptera; Notonectoidea.

British representation. 4 species in Britain; genera 1. Notonecta. E.g., N. maculata (Spotted Boatfly, Spotted Back-swimmer).

Illustrations. • Notonecta maculata (Spotted Boatfly, Water Boatman, Back-swimmer: B. Ent. 10. • Notonecta maculata (detail: B. Ent. 10. • Notonecta maculata (dissections: B. Ent. 10. • Notonecta maculata (legend+text: B. Ent. 10. • Notonecta maculata (text: B. Ent. 10, cont.. • Notonecta glauca, N. maculata, N. marmorea, N. obliqua (Southwell & Leston). • Notonecta glauca, with Corixidae, Plea and Ranatra: Saunders (1892)..

To view the illustrations with detailed captions, go to the interactive key. This also offers full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, and distributions of character states within any set of taxa.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 2003 onwards. Insects of Britain and Ireland: the families of Hemiptera. Version: 16th May 2016.’.