Small creatures of water and soil: can you identify them?

Count its legs Count its legs. No legs and it is a mollusc, a worm or a larva. Six legs, an insect. Eight, an arachnid. Fourteen, a crustacean. More than fourteen, a myriapod. This one question sorts almost everything.

Fourteen Fourteen, that is seven pairs. It is a crustacean, and the only one commonly found out of water. Note that in water the key counts crustaceans from ten legs, that is five pairs: the threshold is not the same from one habitat to another.

An arachnid An arachnid. In the soil, that includes the spider, the long-legged harvestman, the tiny pseudoscorpion and the mite.

A myriapod A myriapod. The key lists five: the millipede, the pill millipede and the flat-backed millipede, which eat dead leaves, fungi and plant debris, then two predators, the soil centipede and the stone centipede, which attack worms, slugs and insects.

Molluscs Land molluscs, of the gastropod family. No legs, so the key places them straight away with worms and larvae.

To build its shell To build a solid shell. That is why there are more of them on limestone soils, which is handy in the Jura.

Rainy days and cool nights Rainy days and cool nights, when they put out their tentacles. Looking for snails in fine dry weather means looking for empty shells.

The snail climbs, the slug buries itself The snail climbs a wall or the top of a stem to escape the heat of the ground and waits in its shell. The slug has no shell: it buries itself.

Tip upwards, opening facing you Tip upwards, opening facing you. It is the convention in all the keys, and the only way to tell whether the opening is on the right, dextral, or on the left, sinistral.

The colour of the lip The colour of the lip, that is the thickened edge of the opening: usually pale in the garden banded snail, usually dark in the grove snail. It is the only feature the key uses to separate these two species.

More than five hundred More than five hundred, some of them no bigger than a millimetre. For the smallest, you have to sieve the soil and get out the hand lens.

A bit of everything, including dead animals A bit of everything. The smallest graze microscopic algae on tree trunks and grasses, others munch leaves and fungi, some hunt other species, and none turns down fresh droppings or a carcass.

The rim of the opening The rim of the opening. When it is thick, it is called the lip. The line between two whorls is the suture, and all the whorls together form the spire.

Release them exactly where you found them Exactly where you found them, and soon after you have finished looking. Moving them, even a few metres, puts them in a habitat they did not choose.

An hour at most No more than an hour, to limit the impact on the habitat. That is the recommendation of the keys themselves, and it is rarely followed.

Put it back Put it back. This layer of leaves is the habitat, not just a lid: without it, whatever lived underneath dries out.

Some eat the others Because some eat the others. The diving beetle, its larva and the water scorpion attack larvae, tadpoles and small fish. Sharing does not end well.

Sterilise it, thirty minutes in the sun Leave it in the sun for thirty minutes to sterilise it. Otherwise you carry bacteria and fungi from one pond to another, which is how some diseases spread.

At least ten At least ten, that is five pairs. It is the group of the freshwater shrimp, the water louse, the water flea and the crayfish.

A pond skater A pond skater, four centimetres, or the water measurer, three centimetres. The key places both among the insects found on the water. The diving beetle and the water boatman live in the water, not on it.

The caddisfly larva The caddisfly larva. It builds its case from whatever it finds, which makes it the most recognisable of all aquatic larvae.

Nothing at all Nothing. As an adult it does not feed, just like adult stoneflies and caddisflies. Their whole feeding life was spent underwater, as larvae.

A worm A worm, so no legs. It feeds on invertebrates and fish blood, and can reach six centimetres.

A twelve-centimetre mollusc A mollusc, the swan mussel, with no legs at all, which can reach twelve centimetres. It feeds on plant plankton and tiny plant debris.

No, unless you have a state exemption No. Aquatic habitats shelter protected species, and handling them without an exemption issued by the state is prohibited. This also applies to dragonfly and damselfly larvae.

An anuran An anuran. It is the very first question in the amphibian key: tail or no tail. Urodeles are salamanders and newts, anurans are frogs and toads.

Yellow spots Yellow spots. The fire salamander has them on its belly, flanks, back and throat. The Alpine salamander is entirely black, with no spots at all.

The great crested newt has small white dots on its flanks The great crested newt has small white dots on its flanks, the Italian crested newt does not. Both have a yellow to red belly with dark spots.

The Alpine newt The Alpine newt. The palmate newt also has an unspotted belly, but yellow to pale pink.

Its heart-shaped or teardrop pupil Its heart-shaped or teardrop pupil, unique among our amphibians. The midwife toad has a vertical pupil, and the common toad a horizontal or round one.

The shape of the snout The shape of the snout: long and pointed in the agile frog, short and rounded in the common frog. The dark brown band between the eye and the eardrum is common to both.

No, it takes genetic analysis or its call No. The key stops at undetermined green frog: identifying the exact species takes a genetic study or its call. It is one of the rare cases where a field key admits its limits.