The fauna of North American temperate cold springs: patterns and hypotheses

SUMMARY. 1. The relative abundance of six classes of macroinvertebrates in fifteen mid‐Appalachian and thirteen other North American cold springs is briefly reviewed. In both surveys peracaridans, molluscs, and triclads dominated the hard‐water limestone springs, whereas insects dominated the relatively acidic soft‐water springs. 2. A hypothetical framework is offered to explain the dominance of non‐insect taxa in hard‐water limestone springs. The importance of a non‐emergent lifestyle and high population densities in springs is emphasized. Some evidence is offered in support of the proposed hypotheses, but most of the testing remains to be done.