Carefully examine the contents of your tray and see how many different types of animals you have caught. Try to identify the different animals by using “The Freshwater Name Trail” or other identification guides. Observe the variety of creatures: some will be quite large, others very small; some move quickly, others hardly move at all. Watch how they move, and try to see how they feed.

Look for clues about how they breathe – some simple small animals can absorb enough oxygen directly through their body surface, but can you see breathing tubes attached to the surface of the water (e.g. mosquito larvae), or feathery gills to absorb oxygen directly from the water (e.g. mayfly nymphs), or silvery air bubbles carried against their body (e.g. water beetles)?

Although many of the animals you have caught will be insects, some of them will be other types of invertebrate (and you may even have caught a few vertebrates such as tadpoles or young fish). Among the non-insects in your tray, look out for the following.

Flatworms. Flatworms are usually found on the bottom of ponds or streams. They feed on small animals, such as crustaceans and insects, alive or dead.
True worms. Several types of small worm live in mud at the bottom of ponds and streams, feeding on detritus (dead plant and animal material). Bright red Tubifex worms are an indicator of polluted water.
Leeches. Leeches are commoner than you might think. Most of the ones you are likely to see feed on other small invertebrates, such as shrimps or snails.
Molluscs. You may find small pea mussels (larger bivalves are usually only found in lakes and rivers), but you are almost certain to find some aquatic snails of various sizes and shapes.
Crustaceans. Freshwater shrimps and hoglice are quite common in ponds, where they feed on detritus. If you look carefully, you may see small ‘water fleas’ such as Daphnia or Cyclops.
Arachnids. True water spiders live under water, where they create a diving bell out of silk to hold their own supply of air. You might also see the non-aquatic wolf spider Pirata piraticus walking on the surface of the water. If you are keen-eyed you may see tiny carnivorous water mites.

Most of the animals you find, however, are likely to be insects, with their characteristic six legs. Many of them will be the underwater immature stages (nymphs or larvae) of adults that fly over and near the water – where they will lay their eggs – and that are often seen perching on plants beside the water. You should refer to “The Freshwater Name Trail”, or other keys and illustrated books, to identify the insects in your collecting tray (or the ones that you have seen on nearby vegetation or flying over the water). Many different types of insects live in our ponds and streams, but most of the common species belong to one of the following groups.


Mayflies are usually found in clean fast-flowing streams, but several species are common in ponds. They are all very sensitive to pollution. The aquatic nymphs of most species feed on algae growing on waterweeds or stones, but some species burrow into the bottom mud and feed on detritus. Uniquely amongst insects, it has a sub-adult stage that can fly (known by fishermen as a ‘dun’), but moults again into the full adult soon after it has emerged from the water. The males usually emerge first and swarm in the air above the water – sometimes in very large numbers – waiting for the females to emerge. Their adult life is very short.

The nymphs and adults of dragonflies and damselflies are fiercely carnivorous. They commonly prey on other insects, but large dragonfly nymphs are also capable of catching and eating tadpoles or small fish. The nymphs of most species are sensitive to pollution. Most dragonflies and damselflies live in the still or slow-moving waters of ponds, ditches and canals, but a few dragonflies and the demoiselle damselflies are found in the running water of streams. Adult dragonflies often fly long distances away from water in search of prey.

Stoneflies are mainly associated with clean fast-flowing streams, though some are found at the edges of large lakes and one common species lives in ponds. Most stoneflies are very sensitive to pollution. The nymphs are often found under stones on the bottom of unpolluted streams: when they are disturbed, they crawl away quite slowly. The nymphs of most species feed on plant material or detritus but some large nymphs are carnivorous.

True bugs all have piercing and sucking mouthparts and most bugs found in ponds are carnivores in both their nymphal and adult stages. Some – such as the pond skater and water measurer – live on the surface of the water and feed on animals trapped in the surface film. Others – such as the greater water boatman and water scorpion – live under the water and hunt for small animals.

Moths are not usually thought of as freshwater animals, but a few species of the family Pyralidae – the china mark moths – have larvae that feed on aquatic plants. When young, the caterpillars burrow within the tissues of floating plants, and later form a case from leaves and silk, in which they live. To find them, look out for floating leaves of pondweed and water lilies with rounded oblong pieces missing from their edges: turn these leaves over and you should find a caterpillar in its case. The adult moths can be seen resting during the day on vegetation at the water’s edge.

Caddis fly larvae are of two types. The first – and best known – make protective cases out of various materials and live within them. These cased caddis flies graze on algae: the ones in ponds usually make larger cases out of fragments of leaves and twigs, whereas those in streams more often make smaller cases using grit and tiny stones. The second type do not build cases. Caseless caddis flies are often carnivorous, and some stream-living ones spin nets to catch their prey in the flowing water. Some of these caseless caddis flies filter tiny particles of food from the water with a silk net. Others are carnivorous and spin snares to catch their prey in flowing water. Some caddis fly species are tolerant of slight pollution.

A variety of true two-winged flies have aquatic larvae. Mosquito larvae hang under the surface film of stagnant water, attached by a breathing tube at their tail end: they are tolerant of polluted water. Non-biting midge larvae feed on detritus. Some of them contain haemoglobin and are therefore bright red: these bloodworms can survive moderate pollution. Rat-tailed maggots – the larvae of drone flies – have a telescopic breathing tube and can survive in heavily polluted stagnant water.

Beetles are the most successful and diverse group of all insects, and many of them are aquatic or semi-aquatic. Reed beetles can often be found on vegetation at the water’s edge. Whirligig beetles swim rapidly on the surface of still water and can sometimes be seen in large numbers making their characteristic gyratory trails of movement. Under the water, the larvae and adults of several species of water beetles may be found. Some of these are herbivores, feeding on aquatic plants, but others – notably the fiercely carnivorous great diving beetle – are voracious predators.

While what you have seen is still fresh in your mind, spend some time thinking and talking about the role of each of the animals you found within the pond or stream community.

In your notebook, about 2 cm from the left of the page, write down a list of the animals that were feeding on aquatic plants or algae (the herbivores), and then the ones that were feeding on detritus and decaying organic matter (the scavengers).
Then, down the middle of the page, write down a list of the ones that are carnivores and try to decide which of the other animals they were preying on.
Do you think some of the predators were feeding on other carnivores? If so, list them at the right of the page.
In the left-hand margin, write – sideways – ‘Plants’, ‘Algae’, ‘Detritus’.
Now draw arrows to link each type of animal to its likely food. Some plant eaters will also eat algae, and many carnivores eat more than one type of prey: draw as many linking arrows as you think are true.
At the bottom of the page, write two notes to remind yourself that: (a) the plants and algae are fed by energy from the sun; and (b) when plants, algae, herbivores, scavengers and carnivores die, their remains become detritus and decaying organic matter.

When you have finished, you will have drawn a ‘food web’ for your pond or stream, showing how all the organisms interact with each other.

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