These non-native limpets arrived from America in the 19th century and are now widespread in the UK. They form stacks and have a specially adapted shell which, when flipped upside down, looks like…

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.

The keeled skimmer is a dragonfly of heaths and commons with shallow pools. It has a skittish and weak flight, and is on the wing in summer and early autumn.

The black-tailed skimmer is a narrow-bodied dragonfly that can be seen flying low over the bare gravel and mud around flooded gravel pits and reservoirs. It is on the wing from May to August.

The distinctive spiky, or 'bearded', green flower heads of wall barley appear from June to July and are easy to spot in an urban environment as they push their way up through pavements…