While walking along the Tsolum River this week I took the time to turn a few stones in a fast flowing riffle. Under one of the rocks was a pair of mayfly nymphs (Order Ephemeroptera from Ephemeros – short lived and Pteron – wings). While the nymph part of the life cycle can be anywhere from three weeks to two years in length, the Latin name refers to the adult part of the life cycle which is often very short, sometimes only as long as a day. During that period the adult’s single purpose is to reproduce.
Mayfly nymphs are fairly easy to identify. The three long tails (or cerci) and often visible gills along the sides of the abdomen are distinctive. They live in a variety of different aquatic habitats and are either herbivores or detritivores.
The neat thing about finding them in the Tsolum is that they are very sensitive to low levels of oxygen in the water, rate of water flow, and chemical pollution. They may be a sign that the restoration work done by the Tsolum River Restoration Society is having a positive effect on the health of the river.