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.
Source: Epiproct And Dorsal Process Structure In The Allocapnia Forbesi Frison, Allocapnia Pygmaea (Burmeister), And Allocapnia Rickeri Frison Species Groups (Plecoptera: Capniidae), And Inclusion Of Allocapnia Minima (Newport) In A New Species Group
Male epiproct. Apical segment of upper limb ca. 345 µm long, armed on apical ca. 154 µm with dense patch of wave-like spikes (Figs. 73 - 76); apical segment ca. 135 µm wide at base, tapered to a rounded tip. Basal segment of upper limb ca. 355 µm long and ca. 102 µm wide at mid-length; basal segment with median groove. Greatest width of lower limb ca. 200 µm; lower limb bearing a sparse, marginal row of long setae in apical third. Male tergal process. Prominent raised structures on abdominal terga 7 and 8 (Figs. 77 - 78). Process of tergum 8 tri-lobed with mesal lobe about as high as lateral lobes; tergum 8 process ca. 176 µm wide; lateral lobes expanded on dorsum in lateral and dorsal aspect, appearing somewhat boot shaped in side view; anterior face of process with a transverse groove. Process of tergum 7 only slightly elevated, ca. 75 µm wide, and without mesal lobe.