Thanks to Blaine Mathison at BugGuide.net for confirming my ID.
Weverton/C & O Canal, Washington County, Maryland; Harpers Ferry quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Thanks to bugologist1 at BugGuide.net for the ID: https://bugguide.net/node/view/1942937#3817926
Thanks to Chris Angell at BugGuide.net for the ID: https://bugguide.net/node/view/2367209
Still alive but not flying--possibly hit by a car.
Elevation c. 680m
Adkins Arboretum, Caroline Co., Maryland; Ridgely quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Rachel Carson Conservation Park, Montgomery County, Maryland; Sandy Spring quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Thanks to Bill Dean at BugGuide.net for the ID: https://bugguide.net/node/view/2381952#3802992
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Adkins Arboretum, Caroline Co., Maryland; Ridgely quad
New genus for MBP!
Some members of the family "possess chemical defenses and advertise them with bright aposematic colors." (BugGuide).
Thanks to Frans Janssens at BugGuide.net for the ID: https://bugguide.net/node/view/2363056/bgimage Frans indicates this may be N. persimilis.
Adkins Arboretum, Caroline Co., Maryland; Ridgely quad
Adkins Arboretum, Caroline Co., Maryland; Ridgely quad
Flies in this group require dissection to identify to species.
Thanks to John F. Carr at BugGuide.net for the ID: https://bugguide.net/node/view/2116009
Patuxent River State Park â Elton Farm Rd., Montgomery Co., Maryland; Sandy Spring quad
New species for MBP and the first mid-Atlantic record on BugGuide!
Thanks to Diane Young at BugGuide.net for the ID: https://bugguide.net/node/view/2283676
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Thanks to Ken Wolgemuth at BugGuide.net for confirming the genus ID: https://bugguide.net/node/view/2341538#3747996
Banner's Overlook, Greenridge State Forest, Allegany County, Maryland; Paw Paw quad
A. fuscus or A. holomelas? Is the latter a recent split? It is not in my books.
Walindi Plantation Resort, New Britain, Papua New Guinea
Cranesville Swamp Natural Area, Garrett County, Maryland; Sang Run quad
Russell Rd., Garrett County, Maryland; Barton quad. Circa 2900 feet elevation.
This looks like it might be in the S. coeloptera group given eye/head shape and orientation?
Ten Mile Creek, Black Hill Regional Park, Montgomery Co., Maryland; Germantown quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Population is still hanging on here along Big Run, where it is partial to hemlock forest and uses Cardamine diphylla as a host plant.
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Asociacion para La Conservacion de Aves y La Biodiversidad Koepcke's Hermit, San Martin, Peru
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
I think this is S. brevicornis. (BugGuide.net confirmed the genus but not the species).
Catoctin Mountain Park, Frederick County, Maryland; Blue Ridge Summit quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
In coniferous/deciduous forest near a brackish water marsh. maybe Orchestia grillus?
Chesapeake Bay Environmental Ctr., Queen Annes County, Maryland; Queenstown quad
Rock Creek Stream Valley Park, S. of Twinbrook Parkway x Veirs Mill Road, Rockville, Montg. Co., Maryland; Kensington quad
Calopteron terminale because (1) transverse depression on elytra, (2) uniformity of ridge heights, and (3) blue tinge. I'm not sure how useful blue tinge characteristic is (from BugGuide page on species). In case useful for anyone else learning about this genus I took a stab at some visual ID tips (on pic #2):
The other two members of the genus in the United States and Canada are Calopteron reticulatum and Calopteron discrepans. I have a blog post with more pics.
Please also see the very similar Caenia dimidiata.
There are many more species (100+?) in Mexico, Central America, and South America but those species are not yet logged into iNaturalist. So if you have observed a Calopteron outside of the United States, keep your ID at the genus level even if it sort of looks like one of the three species in the United States.