This common name refers to only one species.
These are very rarely called Sand Drakes.
In the East and Midwest
this is one of the most important hatches of the Spring. They are large flies which emerge sporadically, making for long days of good fishing.
This species contains the two classic Eastern hatches formerly known as Stenonema vicarium
and Stenonema fuscum
, the "March Brown" and "Gray Fox." Entomologists have discovered that these mayflies belong to the same species, but they still display differences in appearance which the trout notice easily. Anglers should be prepared to imitate both types.