Shadow Darners are fairly large (TL 64-73mm) dragonflies which can be found region wide in a variety of habitats. As the name implies these dragonflies are often found in the shade (the species epithet umbrosa also means shadowy). They are more commonly found flying later in the day, often well into the dusk, and may be relatively absent in the morning. They also persist until much later in the year than other other darners, and have been found flying in our region in December.
Superficially, Aeshna umbrosa resembles all of the other mosaic darners. However the combination of rearward flagged thoracic stripes, paired pale or blue spots on the underside of the abdomen, and the top of S10 all black and lacking a blue spot, is diagnostic for both males and females of this species.
If one intends to try to accurately identify darners, or really any Odonata, I highly recommend getting Dennis Paulson’s “Dragonflies and Damselflies of the West”, and/or “Dragonflies and Damselflies of Oregon” by Cary Kerst and Steve Gordon. They will save you much time and frustration.
Shadow Darner males searching for a mate patrol shorelines closer to the water than other darner species, and regularly hover facing shore for long periods. Females oviposit into muddy banks and woody debris, and for this reason their cerci are often broken off.
Both sexes fly roughly circular beats in shaded alcoves while searching for food. For this reason individuals can often be observed for lengthy periods of time, if they are undisturbed. Because they have smaller spots and are often in shade they look darker than most dragonflies, and it is probably this species that accounts for most of the sightings people tell me about of “an all black dragonfly “.
Size- TL 64-73mm
Habitat- Mostly slow and still water, but can be found near streams and rivers.
Range- Region wide
Eats- Anything it can subdue
Flight Season- June to November