The Sulphur Saga


Why should this insignificant little insect, barely one-half inch tall, cause so much excitement among so many people who care about Spring Creek and its tributaries?  This yellow creature, known locally as a sulphur mayfly, begins to appear in mid May throughout the watershed.  In late afternoon or early evening, the nymph or larval stage, swims from the stream bottom to the surface, splits its outer skin, a graceful winged insect struggles out of its nymphal skin, and flies off to nearby vegetation.  This process is called a hatch.  If only a few nymphs hatched, there would be little notice.  Rather, they hatch by the millions and they attract the attention of nearly every fish in the stream.  As the fish feed voraciously on the nymphs and newly emerged flies, so too are fisherman attracted, as they try to fool the trout with their imitation sulphur flies.  This phenomenon occurs over a period of several weeks.  To many people, it is a marvel of nature.  Perhaps the real importance of the massive sulphur hatches is its link to water quality.  The sulphur is one of the many species in the group of insects called mayflies (Ephemeroptera).  Mayflies do not tolerate polluted waters.  Rather, they are found in lakes and streams that are relatively clean and free of contaminants.  Mayflies may be thought of as indicator organisms.  When one finds large numbers and many different kinds of mayflies, you can be assured that the water is quite clean.  When mayflies are scarce, it is likely that the water is somewhat polluted.  If no mayflies can be found, it is a sure sign that the water is seriously polluted.  These creatures may be small, but they convey a powerful message.


written by: Dr. Robert Carline