Saturday, August 7, 2010

Common Green Darner (Anax junius)

A large darner with a length of about 80 mm, this immature male's abdomen will turn blue with age (a female's abdomen retains the reddish purple hue). The pictures were taken near the marsh bordering the Eastern Ontario Trail. These beautiful insects are often encountered at the north shore of Stoco Lake, where one has a good chance of seeing ovipositing pairs on emergent vegetation.

It's surprising how well camouflaged the dragonfly is despite its psychedelic color scheme. (Said color scheme having evolved over millions of years of natural selection, yet still appealing to the human sense of esthetics. But then again, some people loathe and fear these harmless, and from our point of view, beneficial insects.)

The target shaped mark on top of the head confirms this is indeed a Common Green Darner (Anax junius) and not a Comet Darner (Anax longipes). The latter species is a vagrant in southern Ontario and unlikely to be encountered in this area in any event.

Here's a dorsal closeup of the head of a different immature male portraying the distinctive "bull's eye".

The striking colors and patterning of the Common Green Darner are unique, making this oblique detail view of the cerci unnecessary for identification. Since the profile of the claspers is often vital to distinguish closely related odonate species, it's second nature to me to acquire an image of the terminal abdominal segments whenever possible.