Invertebrates in your pond
There are 51 different kinds of mayflies found in Britain. About 10 of these live in ponds, but by far the commonest is the Pond Olive (shown in the picture) – it's one of the most widespread pond animals.
Pond Olives are particularly fast colonisers: their eggs hatch out as soon as they hit the water. After the eggs hatch mayfly larvae spend several months in the water growing before emerging as a fully grown mayfly.
Pond Olive larvae eat algae that they graze from the leaves and stems of underwater plants. Many people think that adult mayflies only live for a day on land. But not the Pond Olive - it can survive for as long as a fortnight.
Caddis flies are close relatives of moths and butterflies. There are a lot of different species – in Britain around 250, but you need a lot of practice to recognise the different types. The underwater larvae are much easier to see than the adult flies – which look like moths, and are often nocturnal.
Most caddis flies have a case, but not all. Cases are made by gluing bits of plant together with silk, like the one in the picture, or sand grains. Cases give a clue to the identity of species but are not usually the clinching identification feature.
But cased or not, every good quality pond should have caddis.
Most cased caddis larvae graze algae but some are predators. They are quick colonists of new ponds, and several species are happy in ponds that dry out in summer.
Alderfly larvae are predators of the pond bottom, and are happy in silty, vegetation rich environments. They have 6 legs like all insects, but the feathery gills on each segment might make you think they had more.
The adult alderflies emerge from ponds, rivers and lakes in spring and early summer. They are easy to see in spring and early summer – a dark brown and rather tame kind of fly, with its wings held in a tent shape over the back.
There are only three different kinds of alderfly in Britain, and the commonest – the mud alderfly (Sialis lutaria) - is the one that is usually found in ponds. They are one of the animals you expect to see in really good quality ponds.
Dragonflies are quick colonists of new ponds: and are usually present in all good wildlife ponds. They will colonise small ponds, and ponds that dry out in some years.
Usually the first to come are the species like the Common Darter or the Broad-bodied Chaser that like bare sediments. To encourage these species it’s important to try to ensure your pond has bare clay or sand on the bottom for as long as possible. When organic sediments build up they won't be so happy.
In submerged plants you may find the larvae of Emperor dragonflies.
Later on, as your pond gets more silty, these species will probably be replaced by Brown or Southern Hawkers. Dragonflies are predators which feed on other small pond animals.
Almost all our common dragonflies can be found in garden ponds. The real trick will be to see whether in gardens we can make ponds which suit some of the species that need acid peaty water habitats. Most garden ponds aren’t likely to be suitable at present. But if you could make a really acid water pond, complete with Sphagnum moss, who knows? Maybe some of our more endangered species might colonise garden ponds too.
Damselflies are the cousins of dragonflies and ponds are important habitats for them too: more species live in ponds than rivers, and some of the most endangered damselflies live in acid ponds in special places on heathland and in bogs.
A good wildlife pond will nearly always have damselflies, often including two or three common species such as the Large Red Damselfly and the Azure Damselfly.
Like dragonflies, damselflies are predators feeding on any small pond animals they can catch.
Damselflies quickly colonise new ponds. Large Red Damselflies can live in the tiniest garden ponds of no more than a square metre. The adults lay their eggs in trailing grasses and fallen leaves – so don’t pull these out if you want to encourage these animals. Other damselflies need underwater water plants as their main habitat.
Water beetles are one of the most diverse groups in freshwater – in Britain there are around 350 species - but because they are the Little Brown Jobs of the freshwater world many people don’t realise quite how many different types there are.
The picture shows what is one of the commonest water beetles the Common Black Diving Beetle Agabus bipustulatus which is about 1 cm long.
In a good wildlife pond there should be lots of different kinds of water beetles. Between a third and a half of all the species of animals you can see will be water beetles.
Many water beetles are great fliers. They quickly colonise new ponds, and also move between ponds and other freshwaters during the year.
But not all beetles are fast movers: some can’t fly at all, or only when its unusually warm - so can’t easily move from one pond to another. These species are often some of the most endangered because if the place they are living becomes in some way unsuitable they can’t move to a new home.
Don’t forget to look out for water beetle larvae too. Many look a bit like the larvae of alderflies but often have two tails, and they lack the gills along the side of the body that are one of the distinguishing features of alderfly larvae.
The water beetle larva (above right) was found and photographed by Pond Conservation supporter Carol Woodall. It's almost certainly a half grown larva of one of our six species of great diving deetles: most likely either the Common Great Diving Beetle Dytiscus marginalis or the Half-grooved Great Diving Beetle Dytiscus semisulcatus.
The words 'water bugs' are sometimes used as a catch all term for everything that lives under the water. But 'bugs' are really only the group of insects that has piercing mouthparts – like an aphid – and uses it either to feed on plants or animals.
There are lots of different kinds of water bugs that do this. Backswimmers, lesser water boatmen, the water scorpion - it's not really a scorpion, and the water stick insect – which isn’t really a stick insect either!
There are around seventy different species of water bug altogether – including lots of different lesser water boatmen which you might call the little stripy jobs of the pond world.
Most bugs are predators, but not all. The lesser water boatmen collect up fine bits of debris from the bottom of the pond with their special comb like legs.
Bugs are often very good fliers – so they’re usually some of the first creatures to arrive at new garden ponds. Watch your pond on a warm day and you will often see backswimmers taking off.
Water bugs of one kind or another should always be present in a good quality wildlife pond – usually several different kinds. They’re not particularly sensitive to pollution: some can live in the most scummy of places including ponds with lots of bare polluted sediments, with no water plants (many ponds are like this).
In most garden ponds the shrimp that you will see is a small American species introduced to this country during the last century called Crangonyx pseudogracilis (kran-gone-icks sue-doh-gras-i-lis). Unlike lots of species introduced to places outside their normal range, this one doesn’t seem to have done much harm in Britain.
The more familiar river freshwater shrimp Gammarus pulex does occur in ponds with inflowing streams and springs, but isn’t very likely be very happy in most garden ponds.
People believe that freshwater shrimps are good indicators of whether a pond is polluted or not. Actually this isn’t true: they are quite tolerant of all sorts of pollutants, so they can live in good ponds and bad.
Good quality ponds will often have shrimps, especially if the pond has been around for a while. They don't fly so may take many years to arrive at a pond - perhaps as eggs or tiny young ones stuck to birds feet.
Its hard to miss pond skaters on your pond – and practically every pond must have them at some point.
Pond skaters all look very similar to each other but there are actually 10 different species found on ponds and lakes in Britain – and they venture out onto rivers too.
Pond skaters are predatory bugs that mainly go around picking off the dead and unfortunate animals that fall onto the water surface and are trapped there.
The common garden species are all good fliers which can easily move from pond to pond. But they can’t all fly, and when they find a nice spot some of their young will often be a type that doesn’t have wings.
Then as winter approaches pond skaters will also produce young that can fly, and so can move to a winter hibernation spot that’s safe.
There are two other groups of animals that like pond skaters you might see on the water surface. These are the common water striders (Hydrometra stagnorum - Hi-dro-mee-tra stag-nor-um) and one of the two species of Water Crickets (Velia species - vee-lee-aa). Neither skates like a skater: water measures trot about with a high stepping grace like a miniature prancing pony; water crickets scuttle across the water, their little legs going for all they are worth. The truly eagle-eyed might also spot pigmy water crickets.
Water slaters are watery relatives of the familiar garden woodlice. There are only two likely to seen in Britain, and by looking closely at them you can actually tell them apart quite easily: the common water slater (Asellus aquaticus) has two white spots on its head, whereas the more uncommon, slightly classier one-spotted water slater (Asellus meridianus) has only one spot on its head. It’s the common water slater that usually is found in garden ponds: we’ve never seen the one-spotted water slater in a garden pond, though given how little we know about garden ponds it wouldn’t be surprising to see it turn up.
Water slaters have to get around from pond to pond by being moved on plants, or by birds, or floods. But get around they do, although they will probably take quite a few years to arrive naturally in a new garden pond. There’s nothing to really worry about if you don’t have them, and no special need to introduce them.
Water slaters suffer from a common prejudice that they indicate pollution – they don’t. They are a perfectly normal part of the animal community of any fairly alkaline pond. They don’t care for acid water though, so you don’t find them in more mountainous uplands, nor usually in the acid heathland ponds of southern England.
The reason for their polluted water reputation is that in the early days of river pollution studies they were one of the survivors when sewage was discharged pretty much untreated into rivers. This is because they naturally live in places where oxygen levels can be low – but there’s nothing unnatural about that in ponds.
Everyone knows that ponds should have snails, and given a bit of time most ponds will be colonized by them.
There are about 40 different kinds of water snails in Britain, many of which can be seen in ponds somewhere. They vary in size when fully grown from the tiny Nautilus Ram's-horn - just 2 or3 mm across - to the Great Pond Snail which grows up to 4 cm.
We all know snails can't fly but the common water snails are good at getting around from place to place. Most are probably carried in accidentally by birds or perhaps amphibians, and they often introduced when people bring in the sticky eggs attached to bits of introduced plants.
It’s sometimes said that snails are important for keeping a pond clean. It would be nice if this was true: collect a few snails, drop them into your mucky polluted pond and, hey presto, out comes a sparkling shiny wildlife habitat.
Unfortunately, it doesn’t work like this. Snails will thrive in polluted ponds, grazing on a superabundant growth of algae stimulated by excess nutrients. But the chances of the snails cleaning up your pond are nil. To get a clean pond you need to take away the pollutant and the snails don’t do that – they just recycle them around the pond.
Snails naturally need a bit of calcium in the water to grow their shells so in naturally acid ponds - which have very little calcium - they are not a natural part of the fauna. Where there is calcium for them, they will arrive in due course.
Some of our water snails are amongst the most sensitive and endangered of freshwater animals. The Glutinous Snail, for example, which looks pretty similar to the very common and tolerant Wandering Snail, is one of the most endangered animals in Europe. We found some of the last ones in England in a pond near Oxford in the 1990s but sadly it’s gone now. A once quite widespread animal has now become extinct in here - one population is hanging on in Wales.
The Glutinous Snail has become so endangered because it needs the cleanest water – not something that bothers a lot of snails. This clean water is so rare now that the modern landscape is really a very hostile place for the poor old Glutinous Snail.
Lumping all worms, fly larvae, leeches, flatworms and other worm like creatures which people are not very keen on is a bit unfair to these mostly harmless beasts.
Most flies don’t bite (not even most mosquitos), most leeches don’t suck blood (only one – the endangered Medicinal Leech, and even then its bit is painless) and most worms wouldn’t even hurt a fly because they eat mud.
But they do all look rather similar, and a bit wriggly. So it might come as a bit of a shock to realise that there are more different kinds of these creatures living in freshwater – especially the flies – than any other kind of animal.
So take a closer look at pretty yellow and black stripy hoverflies as they dash over the pond and the delicate little non-biting midges with their feathery antennae that are some of the earliest colonists and the beautiful transparent larvae of the phantom cranefly.
Flies and worms also get a bit of a bad reputation because as well as always being present in the nice ponds they can live in some pretty horrible looking places too. They are nature’s hoovers for rotting organic matter. But this is such a diverse group of animals that you can find just about every possible different way of living amongst them: from docile grazers to fierce predators.
One of our favourite animals is the larva of the furry bee mimicking hoverfly – the Drone Fly. Its telescopic snorkel tail is a great way of getting oxygen amongst rotting vegetation that is naturally lacking in this essential gas. But the name we give these creatures does them no favours: rat-tailed maggots. Poor things, it’s not really going to endear them to most people!