I stopped along highway 18 east of Tiger Mountain and south of Fall City to collect some nymphs from this stream. It was simply a convenient spot to look for bugs (if scrambling down a steep, brushy, muddy slope counts as convenient). I have never heard of anyone fishing it. It seems too small and brushy to mess with, though it's large enough to probably hold small trout.
Closeup insects from Holder Creek
Female Baetis bicaudatus (BWO) Mayfly Nymph
View 12 PicturesI collected this one along with a male that was quite a bit smaller but equally ready to emerge in mid April.
I spent (Spent: The wing position of many aquatic insects when they fall on the water after mating. The wings of both sides lay flat on the water. The word may be used to describe insects with their wings in that position, as well as the position itself.) quite a while on the identifications, because they really don't look very much like the Baetis bicaudatus nymph I caught last year in Idaho. However, the presence of hind wing pads (
Wing pad: A protrusion from the thorax of an insect nymph which holds the developing wings. Black wing pads usually indicate that the nymph is nearly ready to emerge into an adult.) rules out Acentrella turbida, the lack of a fringe of long setae (Seta: Little hairs on insects.) on the tibiae (Tibia: A middle segments in the leg of an insect, located between the femur and the tarsus.) rules out Acentrella insignificans, range rules out Heterocloeon and Iswaeon, and the thumb-like projection on the labial palp (
The wing pads on this final instar Baetidae
mayfly nymph are extremely dark.
Palp: A long, thin, often segmented appendage which can protrude from certain insect mouth parts such as the maxillae. Also known as the < />palpus.) points to Baetis. Thus, Baetis bicaudatus is a fairly confident ID, and it's not too surprising that it looked different from my previous specimen because bicaudatus is thought to be a species complex with multiple types that haven't been fully sorted out yet.
The palp on the maxilla of an Ephemerella
nymph (detached and photographed under a microscope) is highlighted in red here.
The microscope pictures for this specimen aren't from the same exact nymph, but a mixture of a few others of the same kind that I didn't mind dissecting.
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