Freshwater leeches of Britain and Ireland
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Freshwater leeches AIDGAP is a photo-based identification guide for naturalists and enthusiasts.
There are 17 species of free-living freshwater leech in Britain and Ireland. Around half of all these can be identified from live animals in the field, while the rest need microscopic examination. This is the first guide to freshwater leeches for many years.
Leeches live in all types of water bodies, from ditches, streams and rivers to lakes, ponds, canals and wetlands. in general there are fewer species in running waters than in standing waters.
So if you’re familiar with pond dipping, then you have probably found freshwater leeches. Often leeches remain clinging to your tray once you have released everything else back to the pond. Hand searching potential habitats is also a useful collection method. Target sites include the underside of stones, the base of reeds and rushes and the wet surface of leaf litter. Your garden pond is a good place to start!
The first stage is to sort leeches into families. There are between one and five pairs of eyes on the upper surface, with the number and arrangement of eyes important for identifying leech families. Then within each family, photographs and species accounts cover field identification where this is possible.
This guide is part of the FSC’s AIDGAP series (Aids to Identification in Difficult Groups of Animals and Plants). Our AIDGAP guides are accessible identification keys, suitable for non-specialists from age 16+. As with all guides in the series, the Adult caddis AIDGAP underwent extensive testing before publication, by beginners and specialists alike.