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Great Water Boatman

Notonecta glauca

Not yet photographed by the community

Swims on its back; predatory; common in garden ponds.

Species Profile

Not Threatened; common and widespread across suitable UK habitats.

Lifespan: 1–2 years
Size & Weight: 13–15 mm long
Habitat: Still and slow-moving freshwater bodies including ponds, lakes, ditches, and canals with aquatic vegetation.
UK Distribution: Found throughout England, Wales, and southern Scotland; resident year-round with populations fluctuating seasonally.
Diet: Carnivorous; actively hunts aquatic invertebrates and small vertebrates by swimming rapidly through water.
Prey: Aquatic insect larvae (chironomids, mayflies), small fish, tadpoles, water fleas, and other aquatic invertebrates.
Predators: Fish (pike, perch, trout), diving birds (grebes, cormorants, herons), and water beetles.
Mating Season: May to September, with peak activity in summer months
Breeding: Females lay eggs individually into aquatic plant tissues or sediment; eggs hatch within 10–14 days; multiple generations per year in warmer conditions.
Behaviour: Highly predatory and aggressive swimmers that hunt at night and rest near the water surface during the day. They are capable fliers and disperse between water bodies. Both males and females produce stridulating sounds during mating.

Did You Know?

•Despite being called 'boatmen', they swim on their backs using their long hind legs like oars, their underside facing the water surface.
•They can deliver a painful 'bite' (actually a piercing proboscis) and should be handled with care.
•They are one of the few aquatic insects that can survive brief periods out of water and may be attracted to lights at night.
•Great Water Boatmen are indicators of healthy freshwater ecosystems and are commonly used in pond monitoring surveys.
•They can remain active throughout winter in UK waters, unlike many other aquatic insects that enter dormancy.

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