Metawee River

ORDER: Ephemeroptera
FAMILY: Ephemerellidae
GENUS: Drunella

The mayfly Drunella is distinguished by its large femoral “biceps” on the front legs. The body rests in one plane with the biceps at the same level as the head and junction with the thorax.

ORDER: Diptera
FAMILY: Simuliidae

What's not to like about blackflies?  Our second most common dipteran.  Rather like a bowling pin with hands attached at the head end.  We have not identified them past family at this point, but it is in the long-term plan.
NABS

ORDER: Plecoptera
FAMILY: Leuctridae
GENUS: Leuctra

Among our most common stoneflies, this family is fairly slender by stonefly standards.  The divergent wing pads are a helpful characteristic. Leuctridae  are similar in overall shape to the Capniidae; however, Leuctridae often do not have pleural folds. If they are present, they only extend from abdominal segments 1-7.  Leuctra  are recognized by abdominal terga with posterior fringes of short hairs and last few segments with longer hairs. NABS

ORDER: Coleoptera 
FAMILY: Elmidae
GENUS: Optioservus

The larvae of Optopservus have a closed coxae, as determined by the straight definition between segments on the ventral side of the pronotum.

The adult Optioservus have a compact appearance, especially the head and thorax. There are also dorsal ridges and a characteristic diamond-shaped feature observable in the dorsal view. SMC

ORDER: Diptera
FAMILY: Chironomidae

 Midge larvae tend to be the most common macroinvertebrate at our sites.  As with other Diptera, there are no true jointed legs.  Chironomids do have a pair of prolegs at each end and preserved individuals tend to curl into a 'C'.  Identification past family requires slide-mounted heads.  We have seen philopotamid caddisflies misidentified with the chironomids and we suspect that that happens when samples are being sorted from trays.  Under a microscope, six prominent legs can be seen on the philopotamids.

© Aquatic Bioassessment Laboratory, California Digital Reference Collection

ORDER: Ephemeroptera
FAMILY: Baetidae 
GENUS: Pseudocloeon 

Mayflies in this genus have a distal lobe on their antennal scapes and the second segment of labial palps has an expanded medial process. Villopores are absent on legs.

© Donald S. Chandler / Discover Life

ORDER: Plecoptera
FAMILY: Chloroperlidae
GENUS: Alloperla

Chloroperlid stoneflies have a cylindrical banded abdomen. When observing their mouthparts, the glossa and paraglossa form a three-pronged (open) notch, and their hind wing pads are parallel (not divergent). Cerci have a vertical fringe of hairs pointing away from the abdomen. Setae on the pronotum are found primarily at the corners.

ORDER: Ephemeroptera
FAMILY: Heptageniidae
GENUS: Epeorus. 

A mayfly with two 'tails'!  This family of mayflies has distinctly flattened heads, and this particular genus has two tails and a unique gill arrangement.
NABS

ORDER: Ephemeroptera
FAMILY: Baetidae 
GENUS: Baetis 

This mayfly has three "tails" and a unique head shape. Its gills are oval shaped and insert dorsally. The wing pad shape is an obvious characteristic. More mature nymphs have long, dark wing pads. SMC

ORDER: Plecoptera
FAMILY: Perlidae
GENUS: Acroneuria

Acroneuria are reasonably common in our samples.  Acroneuria always have three ocelli.