Great Silver Water Beetle 
Great Silver Water Beetle (Hydrophilus piceus
Britain's largest aquatic beetle, growing to a maximum length of up to 50mm, although 40mm is more common. As with many insects the Great Silver Water Beetle numbers have declined recently. These beetles are now one of Britain's rarest aquatic beetles. They can still be found across England in small numbers at ponds, lakes and slow moving water. They are now found mainly in the SE & SW of England. Despite their huge size these impressive beetles are omnivorous and feed mainly on decaying plant matter at the bottom of ponds. The Great Silver Water Beetle lives at the bottom of ponds and can be seen as it takes to the water's surface head first. Oxygen is collected as a large bubble and stored in the beetle's wing-cases before the beetle quickly returns to the bottom of the pond. This trapped air bubble can give the beetle's underside a silvery appearance which is where they get their name. The similar Great Diving Beetle (Dysticus marginalis) comes to the water's surface rear end first. The Great Silver Water Beetle is largely a scavenger unlike the Great Diving Beetle (Dysticus marginalis) which is a ferocious predator.

The predatory larvae can grow to 70mm in length and feed largely on pond snails. Fully grown larvae, of about 70mm in length, leave the pond in late summer to pupate in a silken cocoon in damp marginal soil. Occasionally some larvae have been known to travel up to 200m from the pond to pupate. When disturbed out of water the larvae can emit a loud squeak!

Great Silver Water Beetle

Pond Snails
There are about 40 species of Pond Snail in the UK. Many feed primarily on decaying vegetation but others will readily feed on pond plants such as lillies.

Great Pond Snail 
Great Pond Snail   (Lymnaea stagnalis

The Great Pond Snail is Britain's largest aquatic snail and can grow to a maximum shell length of 70mm, although 50mm is more usual. These snails prefer stagnant water sources with plenty of vegetation. Their shell is long and pointed and when not covered in algae is a creamy-white colour. This species is found across much of Europe as well as other countries including North America and New Zealand. The Great Pond Snail needs to surface regularly to breathe but in the winter they will move to the bottom of the pond where they can take in just enough air through their skin to survive. They contain both male and female reproductive organs so can mate with any other Great Pond Snail or reproduce on their own if necessary. This would allow the introduction of just one specimen to populate a new pond with this species. Their eggs are laid in strings attached to the underside of leaves. They will feed on almost anything including all plants, algae and even their own excrement! 

A fairly small specimen of Great Pond Snail at 40mm in length.

Great Pond Snail 

35mm Great Ramshorn Snails from my garden pond in SE London / North Kent

Great Ramshorn Snail - (Planorbarius corneus  /  aka Planorbis corneus

The Great Ramshorn Snail is the largest European species of air-breathing freshwater Ramshorn Snail. Adults have a large flat shell of around 30-40mm with an almost circular aperture. Shells are usually dark brown with a lighter brown underside and the snail itself can be brown or red in colour. These snails can self-fertilise if necessary but with a very low success rate of around 5% of eggs hatching. Just three years after introducing a single specimen to my pond I now have dozens of adult snails. This species is common and widespread across much of Europe and feed largely on algae, rotting plants and organic matter in ponds, lakes and slow flowing rivers. Adults usually live for three years.

LINK 1    LINK 2    LINK 3

Juvenile 5mm Margined Ramshorn Snail

Margined Ramshorn Snail - (aka Dwarf Flat Ramshorn Snail)  (Planorbis planorbis

The Margined Ramshorn Snail is an introduced species of freshwater snail and is consider a pest in some areas. Adults grow to 9-18mm. The shell is flat and has an almost circular aperture with a distinctive keel on the lower side. Found across the UK in Ponds, ditches, shallow margins of slow-flowing rivers and temporary bodies of water. Margined Ramshorn Snails usually live for 12-20 months. Similar to Planorbis carinatus in appearance and only distinguishable by the aperture.

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male Migrant Hawker nymph
Migrant Hawker Dragonfly Nymph   (Aeshna mixta)

Hawkers are the largest and fastest group of UK Dragonflies. The Migrant Hawker Dragonfly is one of the smaller hawkers, growing to around 63mm in length once they've metamorphosed from a nymph. They are not an aggressive species and will tolerate other dragonflies in their territory. They usually take to the wing in late summer - autumn and can be seen from July right up to November.

Unidentified Dragonfly Nymph

Migrant Hawker exuvia

Dragonflies spend the first part of their lives as water-dwelling insects feeding on smaller insects, small fish, tadpoles and newt efts. When ready to metamorphosise, the Dragonfly larvae climb up the stems of reeds and other water plants and leave the water. They bask in the sunlight and the exoskeleton begins to harden. Once fully transformed, the hardened case of the larvae cracks open at the back, and the newly formed dragonfly emerges. It will continue to bask in the sun until its new wings dry and harden, before taking to the sky for the first time. The empty exoskeleton or exuvia, is left behind still clinging to the plant stem.

Great Water Boatmen (Notonecta Sp)
Backswimmers / Water Boatmen
Water Boatmen species are divided into two groups, Greater Water Boatmen (Notonecta Sp) and Lesser Water Boatmen (Corixa Sp). The Greater Water Boatmen are also known as Back-swimmers, obviously because they swim on their backs. Lesser Water Boatmen all swim on their fronts. All Back-swimmers are carnivorous and hunt down their prey at great speed. They can prey on small fish and tadpoles. Once prey is caught using their powerful front-legs, the Back-swimmer then stabs its prey using its sharp beak. The prey is then injected with saliva via the beak, and the Water Boatmen proceeds to suck out the insides. This beak can also be used as a form of defnce if handled as the effects are reported quite painful. Water Boatmen are competent fliers and may be seen leaving a pond on warm sunny days in search of other ponds. They are often the first species to inhabit newly made ponds. Lesser Water Boatmen are herbivores, feeding on plant debris and algae. 

Tiny 3mm young Lesser Water Boatmen, Corixidae nymphs.

Pond Skater - aka Water Striders
Pond Skaters are often seen in groups darting around on top of the water's surface on ponds, lakes, and slow-moving streams and rivers. There are nine or ten species of Pond Skater in the UK and they range from 1-2cm in length. These delicate bugs are covered in tiny little hairs that trap air bubbles that make the Pond Skater waterproof and help them float on the water's surface. They are equipped with sharp pointed mouth-parts that they use to stab and piece their prey and suck out the internal fluids. Pond Skaters can move at a fantastic pace of over 1 metre per second in short bursts. They prey mainly on insects that have fallen onto the water's surface or become stranded whilst drinking from the water.

Juvenile Common Pond Skater (Gerris lacustris) from my SE London garden pond, September 2020.

The short stubby abdomen of theses juvenile specimens looks quite different from the long elongated bodies of adult specimens. The Common Pond Skater is often one of the first species to colonise newly built garden ponds. Adults have a body-length of around 8-10mm.

Large 15mm Pond Skater with small Mining Bee prey

Large 15mm Pond Skater in my garden pond in SE London 12th April 2020.

11cm juvenile European Eel
European Eel   (Anguilla anguilla)
Commonly known as Brown Eels, or Yellow Eels. These long slender fish are now considered to be critically endangered. They spend much of their lives at the bottom of rivers and streams. They can be found in most types of freshwater environments and may go undetected for many years. Eels have even been known to cross land during rainy periods, to find suitable habitat or prey. They don't feed frequently, but usually prey on insects and other invertebrates when small. As they grow they will take larger prey such as fish and frogs. They have an acute sense of smell and can easily locate dead and decaying fish. The European Eel usually grows to around 40-70cm, but specimens have been know to grow to 150cm!
Once sexually mature, the European Eel travels up streams and rivers and makes its way back to the sea. It will then head thousands of miles to the western Atlantic Sargasso Sea to breed.

There are 37 different species of leech in the UK. The one pictured above is Glossiphonia complanata, one of the smaller and more common varieties. Glossiphonia complanata usually feeds off soft parts of the body of invertebrates such as snails.
Only the largest species of Leech, the Medicinal Leech is capable of piercing human skin and sucking blood. These Leeches have a relatively painless bite and often go undetected. Once they have secured a grip on their host they secrete an anticoagulant to prevent the blood from clotting. Many of the British species feed from amphibians and fish.

Unidentified Damselfly nymph photographed out of water
Damselfly Nymphs
Damselflies lay their eggs in little slits made in aquatic plants. These eggs eventually hatch into tiny Damselfly nymphs. As these nymphs grow they shed their skins several times, until the final slough, which is done out of water. At this stage the nymph climbs up the stem of an aquatic plant and begins its metamorphosis. It will emerge from the old dried skin into a damselfly. Here it will bask in the sun whilst the new exposed skin of the damselfly hardens. Then it will take to the air for the first time.

Azure Damselfly nymph photographed in water

8mm Mosquito Larvae
Mosquito Larvae   (Family Culicidae)
In the UK we have around 30 species of Mosquitoes. Eggs are laid in still bodies of water where the aquatic larvae develop. The larvae do not feed but breath oxygen from the water's surface through a breathing tube at the rear end.

6mm Pond Olive Mayfly breeding in my garden pond in SE London, 5th August 2021
Pond Olive Mayfly  (Cloeon dipterum)

Mayflies have four stages in their life-cycle: egg, nymph, dun and spinner. A dun is an immature winged mayfly, which looks very similar to the final reproductive adult spinner. Spinners are often also referred to as imagoes, and duns also referred to as sub-imagoes. When duns emerge they often float helplessly on the water's surface as they wait for their wings to harden sufficiently for them to fly to safety. A great many duns are eaten at this vulnerable stage. Once able to fly duns immediately take their maiden flight to a nearby place of rest where they will often remain until they moult, to reveal the final adult spinner stage capable of reproduction. The dun stage may last anywhere from a few minutes to a few days, depending on the species. 12-24 hours is the most common length of time as a dun. The adult spinner stage will usually only last the same length of time so adults have just one purpose on their minds, to mate and lay eggs before they run out of time. Some species will only last for as little as an hour or two from when they first leave the water. Even the longest surviving species will only have 4-5 days as a winged insect.  The best way to separate duns from spinners is to look at the wings. The wings of a dun are semi-translucent, with a brown, grey or yellow tinge to them/ The wings of spinners are completely clear and colourless, apart from the coloured veins that run through them.

Copulation lasts just a few seconds and whilst most females will fly down to the water's surface to lay their eggs, some will drop the eggs whilst flying above the water, and some will swim beneath the water's surface to lay their eggs. The number of eggs deposited ranges from 500 to 5000 depending on species. Once mating has occurred the male will die. Females die after the eggs have been deposited and their dead and exhausted bodies can often be seen in large numbers floating on the surface of the water.

The Pond Olive is the most common and abundant up-winged fly found on most small bodies of still freshwater in Britain. They regularly breed in garden ponds and shallow, still edges of streams, but seem to have a preference for small ponds. Adults grow to a body-length of 5-7mm and as with many Mayflies, adults are not just seen in May but can be found from May to October. The adult female Pond Olive lays her eggs on the surface of the pond from late afternoon well into the night. Pond Olives are the only species of British Mayfly whose eggs hatch as soon as they touch the water. The  young nymphs emerge and can immediately be seen swimming, either to the bed of the pond of the outer edges. The larvae feed on algae or pond detritus, whilst the short-lived adults do not feed at all.

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40mm Soldier Fly larvae photographed out of water
Soldier Fly Larvae

The Stratiomyidae family of Soldier Flies contains over 2700 species. The larvae are aquatic and can be found in many wetland habitats including garden ponds. They feed on algae and decaying organic matter. They can be seen slowly swimming at the surface of the water, breathing through their tail which breaks the water's surface. The tail is covered in tiny water-repellent hairs which allow it to break the surface of the water as well as trapping small air bubbles acting as a small air supply allowing the larvae to submerge and breath underwater. When fully developed the larvae will pupate by hardening its skin. These pupae are often in the mud surrounding a pond or lake, but sometimes they will be found floating on the waters surface or on vegetation in the pond.

A 45mm Soldier Fly larvae photographed under water

A 45mm Soldier Fly larvae photographed under water

6mm Bloodworms photographed in water
Non-Biting Midge Larvae / Bloodworms   -  (Chironomidae)
Bloodworms are the tiny red worms often seen in stagnant water. They aren't really worms but are actually the aquatic larvae of non-biting midges from the Chironomidae family. These tiny larvae contain around 50% protein and are a great source of food for fish, newts, tadpoles and many other aquatic predators. Adults, also known as Lake Flies, are very similar in appearance to mosquitoes but lack the mouth-parts necessary to bite humans.

30mm Great Diving Beetle Nymph

Great Diving Beetle Nymph   (dytiscus marginalis)

One of the UK's largest beetles with the adult beetles usually growing to around 35mm and the larvae growing to an impressive 60mm. These beetles are aquatic hunters and feed on a variety of prey including tadpoles and small fish. Adults beetles are competent flyers and usually fly at night when the sky is fairly clear and the moon is visible. They use the reflection of the moon on the surface of water to locate new ponds and streams. This can result in beetles mistakenly landing on wet roads when the beetles confuse them for bodies of water following periods of rain.
Adult female beetles have ribbed wing-cases whilst the males have smooth wing-cases. The males also have small suckers on the underside of their front legs which are used to secure a grip on the female during mating.
One should exercise care when handling the nymphs as their powerful jaws can easily penetrate human skin whilst injecting digestive enzymes, resulting in a painful and long-term injury.

LINK 1     LINK 2     LINK 3

Mud Alderfly Nymph  (Sialis lutaria)

The Aquatic nymphs of the Alderfly can be found in ponds and slow flowing streams. They reside at the bottom of the water in the mud and feed on small insects. The adults emerge around May and are usually around 20mm in length. Adult Alderfly are poor flyers and usually stay around the waters from where they grew as nymphs. Adults do not feed and live from just a few days to two weeks purely to breed. There are three species of Alderfly in the UK with Sialis lutaria being the species usually found in ponds. The different species can usually only be distinguished by microscopic examination of the genitalia or anal plates. Alderflies are dark brown and have grey / brown wings with black veins.

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12mm Pond Saucer Bug
Pond Saucer Bug (Ilyocoris cimicoides)

The Saucer Bug is common across England and Wales and grows to around 12-15mm in length. It's another underwater predator feeding on a variety of prey including tadpoles and small fish. It can be distinguished from a beetle by its overlapping wings and stabbing mouth-parts rather than jaws. They are found at the bottom of muddy, weedy ponds and other bodies of water. In Kent and Sussex a similar species, Naucoris maculatus, has also been recorded, but this species is smaller at 10mm and lighter in colour. The Pond Saucer Bug can walk very quickly on land and will often disperse to find new ponds by walking on land at night.

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Diving Beetle (Agabus cf sturmii) netted 23rd April 2017 on a wetlands site in North Kent.
Diving Beetle   -  (Agabus sturmii)
A common and widespread water beetle that can be found in a variety of water-bodies including ponds and marshes. Adults can be found all year round and grow to around 7.5 - 9mm in body-length. There are several very similar species in the UK making positive identification difficult. During winter they hide under substrate and plant debris at the water's edge. Breeding takes place in the spring and eggs are oviposited in roots and stems of submerged plants. The larvae are fully developed by July / August. Both larvae and adults are predatory but will readily feed on carrion too. 

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12mm juvenile Water Scorpion photographed out of water
Water Scorpion   -  (Nepa cinerea)
The Water Scorpion is an aquatic beetle usually growing to a body length of 3.5 but sometimes 4cm. Adults are dark brown in colour and the juveniles, like the one pictured above, are light brown. These ambush predators are not strong swimmers and rely on hiding amidst vegetation at the bottom of the pond or slow-moving stream and wait to grab passing tadpoles or fish with their powerful front pincer-like legs. They have a breathing tube at the back of their abdomen that is sometimes mistaken for a sting. One intake of air can allow the Water Scorpion to stay submerged for around 30 minutes. Adults can live for several years and can fly if necessary to find new breeding of feeding sites. Nymphs are hairy at first and moult 5 times in the first 8 weeks before they take on adult form. If handled or trodden on these beetles can be quick to defend themselves with their stabbing mouthparts.

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Nine-Spined Stickleback photographed under water
Nine-Spined Stickleback   (Pungitius pungitius)

The Nine / Ten-Spined Stickleback is a small fish found in both freshwater and marine bodies of water. Adults grow to a length of 4-6cm although lengths of 9cm occur occasionally. Males usually live for around three years, and females five years. Despite their name, they can have between seven and twelve spines on their backs, which can be raised and used as a defence tactic to deter predators. These spines are smaller and not as effective as those found on the more common Three-Spined Stickleback (Gasterosteus aculeatus). These Sticklebacks don't have scales, but instead have bony side-plates as armour. The males can develop a black area around their groin in the breeding season. Males will guard fertilised eggs, and even teach their young to evade capture by chasing them around the water.

Three-Spined Sticklebacks photographed under water
Three-Spined Stickleback (Gasterosteus aculeatus)
Britain's most common stickleback fish. These are often found living alongside the Nine-Spined Stickleback and are similar in behaviour. Adults usually grow to a length of 4-6cm although lengths of 10cm can occur with marine specimens.

Gasterosteus aculeatus  - Male top, female bottom

Three-Spined Stickleback (Gasterosteus aculeatus) in my garden pond.

Common Darter Dragonfly

A medium sized dragonfly growing to a length of about 45mm. They are often the last dragonflies to be seen in the UK and can often be found well into November. They are widespread across much of the UK and are also often found quite some distance from water. They will feed mainly on other flying insects that they catch with their sudden bursts of speed. The Common Darter can range in colour from bright red, reddish brown, to brownish yellow. The short, squat larvae grow to around 15-18mm in length and can regularly be found in garden ponds and other small bodies of water, including stagnant or brackish water.

LINK 1     Identifying British Dragonflies

Common Darter Dragonfly nymph on a lily-pad in my SE London garden pond, 6th August 2021

Male Common Darter adult & Common Darter exuvia, photographed at my SE London garden pond 9th August 2021.

The Emperor Dragonfly Nymph

The Emperor Dragonfly is Britain's largest bodied dragonfly and grows to a length of 8cm. It is said to have been on the Earth for 230 million years. It is a very powerful flyer reaching speeds of up to 34mph and can detect prey from up to 40ft away. Most of the Emperor Dragonflies life is spent as a larvae / nymph for  2 - 5 years but once transformed into an adult it lives for just  4-12 weeks to breed.

Even as a nymph the Emperor Dragonfly is an aggressive hunter and will tackle prey as large as tadpoles, small fish, young newts and young frogs. When the nymph is ready to complete its metamorphosis it will climb up the stem of a reed or other aquatic plant and bask in the sun until its skin dries out and splits. It will then emerge from the old skin (exuvia) as a fully transformed dragonfly.