Plecoptera

Insects in the order Plecoptera are also known as stoneflies. As the name suggests, stoneflies are typically found in stony rivers and streams, although some species occur on the shores of stony lakes and in ponds and marshes. Adults are commonly found crawling amongst stones and vegetation on the bankside rather than in flight. They fold their wings flat over their bodies when at rest.

Conservation

A number of stonefly species have been identified as of ‘principal importance’ in the UK. The Northern February Red (Brachyptera putata), which is only found in Britain, is on the list of priority species in England, Scotland and Wales. The Rare Medium Stonefly (Isogenus nubecula) is on the Scottish list of species. The Northern Ireland priority species list includes three stonefly species: Dinocras cephalotes, Leuctra nigra and Nemurella pictetii.

Inclusion on these lists means that public bodies have an obligation to support conservation measures for these species.

Life Cycle

A stonefly begins its life as a nymph underwater, undergoing several moults as it grows. Eventually, the fully grown nymph crawls out of the water and sheds its skin to emerge as a winged adult stonefly. Female adult stoneflies drum their abdomens on a surface to attract a mate. Mating takes place on the ground or on vegetation, then eggs are then deposited onto the water surface, and sink down to the river bed.

Riverfly Monitoring

Volunteers taking part in the Riverfly monitoring projects collect samples of freshwater invertebrates and record the numbers of individuals found within easily identifiable groups. One of these groups is the stonefly larvae, which can be identified by features such as their two long tails and long antennae.

There is also a Plecoptera Recording Scheme to assess the distribution and status of stonefly species — see here.