Tillingbourne Riverfly Monitoring

Olives (Baetidae)

There are at least eleven species of Baetidae and they are quite difficult to identify without the aid of a microscope. They are all very good swimmers and the term 'agile darter' describes them well.

The Tillingbourne has a reasonable number of nymphs throughout the year. The specimen in the photograph is believed to be a Baetis rhodani (Large Dark Olive) and was found in middle beat during September 2005.

Although at times we find good numbers of nymphs there is little evidence of large hatches of adult flies - perhaps we aren't there at the right time!