Incidence of Mayflies in Riffles and Pools

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The aim of this study was to compare the relative incidence of mayfly larvae, nymphs, in pools and riffles. The principal hypothesis was that the number observed in riffles would be much more than that in pools. Samples from 10 sets of pools and riffles were taken in the summer of 2004 in Wales, the UK.


The nymphs prefer high dissolved oxygen level environments.
For the purpose of this study it is necessary to introduce the mayflies (Ephemeroptera) because they are such a primitive order of insects that there is much that is unique about their morphology. This uniqueness has to be highlighted to enable better understanding of the experiments conducted to assist this study and the conclusions derived therefrom.
Simply put mayflies belong to Class Insecta Order Ephemeroptera. They belong to the infraclass paleoptera and have primitive wings that cannot be folded over their backs. Fossil records reveal that they may have evolved during the carboniferous period 280-360 mya and their evolutionary history is closely associated with development of wings in Class Insecta as a whole. Modern day mayflies number about 4000 species distributed among 20 families and most are associated with running water (Brooks, Steve, A Natural History of Dragonflies, Mayflies and Stoneflies).
Order Ephemeroptera is well-distributed across the globe except for the two polar regions - the Arctic and the Antarctic - and oceanic islands though it is well-represented in New Zealand (Order Ephemeroptera, "Soil & Water Conservation Society of Metro Halifax" Website, 2004).
The name of the orde ...
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