Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.
Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.
A medium-sized species resembling S. berenice (now a synonym of Siphlonurus typicus), but with more clearly defined ventral markings.
Head brown, frontal margin pale. Thorax brown; pleural sutures pale yellowish. Legs pale yellowish brown, the fore legs somewhat darker. Tips of femora and tarsal joinings dark brown. Wings hyaline; veins brown.
Abdomen brown dorsally; anterior margin of each tergite semi-translucent, yellowish. Traces of dark dorsal and submedian longitudinal dashes visible on the posterior tergites. Pale yellowish ventrally. Lateral dark patches present. Sternite 9 largely dark brown. Forceps base pale yellowish; forceps smoky brown. Tails pale yellowish, joinings brown. Penes shown in fig. 122.