Arrowhead is an aquatic plant of shallow water and slow-moving waterways. In bloom over summer, it displays small, white flowers, but it is the arrow-shaped leaves that are most distinctive.

Famed for its tapping in the middle of the night, supposedly heralding tragedy, the Deathwatch beetle is a serious wood-boring pest. In houses, their tunnelling can cause major damage.

The rose-red breast, large black cap and thick bill make the bullfinch easy to identify. A plump-looking bird of woodlands, hedgerows and orchards, it also frequents gardens.

The chocolate-brown, plump dipper can often be seen bobbing up and down on a stone in a fast-flowing river. It feeds on underwater insects by walking straight into, and under, the water.

Living up to its name, the hairy violet is covered in fine hairs. Look for its delicate, violet flowers blooming from March to June on chalk grasslands, in particular.

Piddocks are a boring bivalve. No, we don't mean dull... we mean that it bores into soft rock, creating a burrow. In fact, they're the opposite of dull - they glow in the dark!

The sparrowhawk is a small bird of prey that can be found in all kinds of habitats and often visits gardens looking for its prey - small birds like finches, tits and sparrows.

A handsome fish, the tench has olive-green flanks, powerful fins and distinctive red eyes. It can be found in lowland lakes and slow-flowing rivers around the UK.

Water-cress has become so popular as a salad addition that it is now cultivated on a wide scale. In the wild, it grows in shallow, fast-flowing streams and is an indicator of clean water.