The vast majority of animal life associated with waterways and wetlands is invertebrate, from the simplest protozoa and worms to molluscs, spiders and insects, and ranging from the rather unpleasant to the spectacularly beautiful. They form the complex and mainly hidden part of the food chain, a jungle of carnivorous, herbivorous and detritus- feeding organisms, vital for the health of the habitat. If the vegetation, water and other factors such as light or shelter are favourable, the species should eventually arrive. They can be helped, for example when restoring a pond, by introducing individuals from a nearby productive pond.
Some habitats are managed specifically for the more spectacular invertebrates, particularly dragonflies and butterflies. Wicken Fen in Huntingdonshire has long been managed for the Swallowtail butterfly, which requires Milk Parsley (Peucedanum palustre) on which to lay their eggs. Dragonflies suffered a decline due to the draining of wetlands and the in-filling and tidying of ponds. Always contact the local office of English Nature (or equivalent) before doing any pond clearance work, as the importance of the habitat for invertebrates is difficult to assess without expert help.
