THERE is nothing like a tranquil Lancashire stream. Between Roughlee and Blacko there is a small lay-by close to a rather ugly but functional bridge. Ignore this, cross the stile and turn right along the stream.

This leads into Bell Wood but in the summer the aroma of flowers and the sound of the rippling water is a joy.

This is a lovely safe place for children (of all ages) to enjoy a pond dip. I always taken a small net and a white plastic dish. I soon found mayfly larvae easily distinguished by having three tail-like structures. Mayfly larvae cannot tolerate even "mild" pollution and so their presence here tells me that the water is clean.

These creatures and also stoneflies which have two tails are easy to see. They have been used by schools as part of the curriculum dealing with water pollution.

Mayflies only live for a couple of days as adults and this account for the fact that they are listed as Ephemerata. The nymphs are certainly not ephemeral and live for more than a year in the water providing it contains plenty of oxygen.

The precise period spent in the water depends upon the species.

For those who want to study the creatures found in freshwater in detail the best bet is to buy a simple book and then get dipping!

You can enjoy delightful scenery at the same time so take a picnic.