|scientific name Notonecta undulata |
Complete life-cycle in urban or rural open pools with plants/debris, adults feed in any lentic system.
Two broods per year, mid-May and July. Those hibernating can live through next August.
Notonecta 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).
Eggs are 1.6-2 mm long, pearly and ovaltine with a hexagonal pattern on the chorion. Hatches after 12 days in spring, six in summer (Hungerford 1917b). Lives in primarily fishless ponds (Streams 1987). Oviposition is on the surface of plants and even large aquatic invertebrates (Hungerford 1917a,b). Ova generate after hibernation and 5 nymphal instars require ~50 days to development (Rice 1954). Adults hibernate in 10-13 centimeters deep in the benthos (Clark 1928), can survive up to six weeks in damp leaf litter (Hungerford 1917). Upper water column ambush predators lighter than water, N. undulata minimizes its swimming time by adhering to objects and capturing prey with short pro- and mesothoracic legs (Streams 1992). Pools housing mosquito larvae may be visited by adults. Conditions of low food availability and complete surface coverage by primary producers preclude N. undulata from oviposition in pools, not water turbidity (Clark 1928). Pesticides reduce survival (Relyea 2005).
Not a concern.
First instar nymphs feed on small diptera, crustacea and ostracoda, and collembolan are included in the second instar (Giller 1986). The third through fifth instars prey on increasingly larger items, including mosquito, Tabanid (horse flies) and dragonfly larvae. Fifth instars are important surface scavengers and adults will eat anything they can subdue, including small fish (Clark 1928).
Common across North America (Hungerford 1917), from the boreal to short prairie biomes in Alberta.
John Acorn (2012-02-20)
Hi Danny, Adult Buenoa spp. are smaller than N. undulata, although arguably less elegant! John
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