Friday, September 5, 2014

Easily identified Aeshna

In contrast to the difficult to distinguish females of the Lance-tipped Darner and Black-tipped Darner, the following two dragonflies are distinctive and can often be identified in flight if seen at close range. The females of both species are colored and patterned pretty much like the the males.

Shadow Darner (Aeshna umbrosa), male – photographed in early September

Habitat – Tweed, Ontario: a marsh west of town, bordering the Eastern Ontario Trail (44.46889°, -77.31528°). Typical local wetland with rushes, Cattails, Arrowheads and other emergent vegetation, the predominant shrubs are Speckled Alders and various species of Willow
Behavior – prefers to fly over small open areas of water among the alders and willows

– the narrow yellowish-green thoracic stripes are recurved at the top (underneath the wings), resembling walking canes
– relatively small greenish abdominal spots, giving the dragonfly a darker aspect than other local Aeshna spp
– the spatulate cerci appear similar to those of the Lance-tipped Darner when viewed laterally, but are wider and look very different in dorsal view
– no cross-stripe on the face, or a very thin brown line at most

A green form female Shadow Darner encountered in late September.

Mottled Darner (Aeshna clepsydra), male – photographed in early September

Habitat – Tweed, Ontario: Stoco Lake, east of the boat pier (44.474563°, -77.306227°). Sand and mud bottom, relatively shallow stagnant water, emergent plants such as rushes, White Water Lilies, Wapato and Pickerelweed
Behavior – forages low amidst the rushes and other emergent vegetation along the lake shoreline

– the lateral sides of the thorax are mottled in yellow, green and blue
– relatively large light blue abdominal spots, giving the dragonfly a much paler aspect than other local Aeshna spp
– the cerci are straight and unadorned, with a small spine at the tip
– the face has a dark cross-stripe

The Mottled Darner might be easy to identify, but it is a difficult dragonfly to find, an uncommonly encountered odonate at best. It was a real privilege to watch three of these dazzling darners foraging only a half a meter away, flitting just above the water among the emergent rushes near the boat pier (there were others flying further east among the rushes and Pickerelweed, but not close enough to be absolutely certain they were indeed Mottled Darners). The last known encounter in the Tweed area was on September 24th, 2009.