Aquatic insect faunas of intermittent streams with an analysis of strategies allowing utilization of these habitats

Knowledge of the survival mechanisms of aquatic insects in intermittent streams is crucial to the understanding of the ecology of these habitats. Intermittent and permanent sections of three small streams in Knox County, Tennessee were sampled for fourteen months in an attempt to determine the survival strategies of the insects present. This information, along with data from previous studies, was used to analyze the survival strategies.

It was found that Cordulegaster erronea and C. obliqua were able to survive the dry period as nymphs in the substrate, and that Ameletus l ineatus and Amphinemura delosa were apparently able to use an egg diapause. Larvae of Pycnopsyche gentilis, Tipula sp. and Tabanus sp. were found in the dry substrate of an intermittent section.

The most widely used mechanisms are diapausing or drought resistant eggs, and larvae or nymphs in the substrate. Other mechanisms that have been found are nymphal diapause, imaginal diapause, prepupal diapause, pupae or adults in the substrate, adults or larvae in earthen chambers, in permanent pools and seeps, as adults encased in silt, as eggs laid above the water, by spending the dry period in permanent rivers and then migrating upstream, as a final instar that leaves the water and becomes terrestrial, and as terrestrial adults.