SeasonalityTwo broods per year, mid-May and July. Those hibernating can live through next August.
IdentificationNotonecta undulata (10-12 mm) is the smallest, most elegant of the adult Albertan notonectids (10-12 mm), and is pale rather than all white (Brooks and Kelton 1967). The black scutellum, occasionally with light spots at the apex, and pale hemelytra blend in with the sky when seen from below. The ventral surface is dark, blending in with the sediments when seen from above. Using a microscope or powerful hand-lens, one can see its hairy central keel on the underside of the fourth abdominal sclerite. This differentiates N. undulata from the two other Albertan notonectids, N. kirbyi and N. borealis (Brooks and Kelton 1967). In the boreal region only one species, N. borealis may be confused with N. undulata. Notonecta borealis is a larger (12-14 mm) and predominantly white species, not pale yellow or light green. Other than its smaller size and thinness, brown anterior femurs differentiate N. undulata from N. borealis, which has brown coxae in addition to femurs brown on the ventral-side (Brooks and Kelton 1967). South of the Edmonton region in the Alberta prairie zones, N. kirbyi can be differentiated by size alone. It is the largest species in Canada (12-15 mm). The hemelytra of N. kirbyi are also distinctive: hemelytra membranes are black at the anterior portion but fades clear towards the tip and there are broad, cloud-like bars which stretch across the clavus to the cuneus. Alternatively, N. undulata wing membranes are pale with a large, irregular spot on the median line (Brooks and Kelton 1967). The only Albertan species of Anisopinae, Buenoa confusa, can be diffentiated from all Notonectinae by its three segmented beak and antennae, smaller size (5-8mm) and shininess (Hungerford 1917 a, b, Brooks and Kelton 1967). Notonecta undulata is synonymous with N. punctata Say, N. (Paranecta) undulata, and N. undulata var. charon Kirkaldy (Henry and Froeshner 1988).