A Dragonfly is "Born"

The word "born" is being used here with poetic licence, as dragonflies are not born in any literal sense of the word. In the course of their life cycle they go through incomplete metamorphosis, and don't be mislead by that word "incomplete". The metamorphosis is incomplete only insofar as odonates don't pass through a pupal stage, but otherwise the change is very complete indeed, and when one compares the naiad to the adult dragonfly it's hard to believe they are formed from the same DNA.

This is a Dragonhunter, Hagenius brevistylus, and with a length of 75 mm to 90 mm it's one of our larger dragonflies. As its name suggests in addition to large butterflies and moths Dragonhunters prey on other dragonflies. A picture is worth a thousand words, here's the story of a dragonfly's journey to adulthood, with the first signs of emergence occuring shortly before 11:40 AM ...

11:40 AM

11:42 AM

11:43 AM

11:45 AM

Time out for a brief interlude here – I've always wondered what the white "strings" (visible near the thorax) on the exuviae might be. I did read on a blog or website somewhere or other that they are involved with the changeover of the insect's breathing system, but couldn't understand what or how switching from internal gills to pairs of spiracles on the abdomen had to do with these string-like structures. So I posed the question in an Internet group, and here's the response ...

"The internal tracheal system is 'closed', which means that the spiracles (openings to the outside) are sealed in the nymph, but must obviously open at the time of the adult moult. The tracheal system extends throughout the body and in the adult opens to to outside through spiracles in the thorax and the abdomen. In the adult the thoracic trachea are very well developed because of the very high oxygen requirements of the flight musculature and hence the evidence of them in the exuviae is particularly obvious. How or if the naiads shed the lining of these tubes in their aquatic moults is a mystery to me. Perhaps the spiracles open at that time to allow moulting.

The internal tracheae serve as the transportation system throughout the body for the oxygen picked up from the water through the thin cuticle of the gill. (Yes, insect rectums are also lined with cuticle.) I don't know how much of a role in oxygen transport the blood plays, but in most larger insects other than bloodworms it is fairly minor. In damselfly naiads you can see the branches of the tracheal system throughout the external gills, hence the term 'tracheal gills'."

And there we have it. The naiad not only morphs from a wingless underwater crawler to one of the most superlative fliers in the natural world, and somehow that amazing prementum which shoots the jaw out to grab passing prey turns into the much different (but just as deadly, from an insect's point of view) jaw structure of an adult, but the insect's entire breathing system changes over as well. In a case like this maybe a picture isn't worth a thousand words after all, because it can only convey a pale shadow of what's really going on here ... and so much for the "brief interlude", now back to the show ... 11:47 AM ...

11:52 AM

11:58 AM ... the teneral dragonfly is free of the exuviae.

12:01 PM

12:11 PM

12:22 PM

12:48 PM

12:54 PM ... the wings are fully deployed. We left at this point and returned at 1:16 PM, by which time the teneral dragonfly had already taken its maiden flight into the shoreline shrubs. The time from when the naiad's exoskeleton first split to flight – about an hour and fifteen minutes.

The exuviae was collected for future reference, in fact it was the discovery of a Dragonhunter exuviae about two or three days old that suggested it might be a good idea to keep an eye out for molting naiads. Whilst this one was about half way through its growing pains another naiad crawled ashore to make its own transformation.

The flattened, dead-leaf-like Dragonhunter naiads and exuviae are unmistakeable, they are a good healthy 40 mm long and have the enlarged third anntennal segments characteristic of clubtail naiads (the two rounded nubs at the front of the head).

So folks – tune in and watch for the next exciting installment of this adventure, it's been ongoing for nearly 300 million years, and still happening at a wetland or river near you ...

The Dragonflies of Drag Lake

Drag Lake is located about 7.25 km west of Tweed , at 44.443129°, -77.391084° along the trans-Canada Trail according to Google Maps. The lake appears to be rock-bottomed – calcerous, judging by the surrounding geology – with relatively shallow water, and the parts of the shoreline are bordered by marshes. Some odonates can be particular with regard to their habitat requirements and for whatever reason the Dusky Clubtail is plentiful at this body of water.

With a length of 50 mm ± 5 mm, Gomphus spicatus is larger than the Lancet Clubtail (44 mm ± 5 mm). As its name suggests the Dusky Clubtail tends to be darker than its cousin, lacking the Lancet Clubtail's yellow dorsal stripe on S9.

However, the dragonflies can vary in color and Gomphids are notorious for their mutable chromatic complexions in any event, with yellow becoming green and eventually changing to bluish-gray with increasing age. Both the Dusky and Lancet Clubtails can sport a pale yellow streak on S9 making this unreliable means of separating the two species. For a positive ID it's necessary to examine the claspers and/or genitalia.

Like most Gomphidae a.k.a. Clubtails, Dusky Clubtails perch on the ground or other horizontal surfaces such as low leaves. They are fairly tame (the individuals in these photos were captured by hand) and can often be approached closely, whereupon the lateral spines on the male's cerci are clearly visible.

The cerci also have a distinct ventral spine.

The male's secondary genitalia, looking at this picture the words such as baroque, labyrinthine and convoluted come to mind ...

The abdomens of the females tend to be more robust than those of males. The distribution of the sexes was rather odd, with thirty one males but only two females being encountered.

A macro of the female's genital plate.

There were plenty of exuviae scattered along the shoreline but none belonging to the Dusky Clubtail were in evidence. Although unconfirmed as yet (the images are at BugGuide.Net) the largest exoskeletons probably belonged to Epitheca princeps, the Prince Baskettail – but no Prince Baskettails were seen flying.

EDIT ... the response from BugGuide.Net: if there are four setae on the edges of the palps (which there are) the exuviae belong to Epitheca princeps. Also, according to this key at Odonata Larvae of Michigan the dorsal surface of prementum should be setose, which is the case in the specimens. So Epitheca princeps it is.

Four teneral female Calico Pennants (Celithemis elisa) were also sighted perching in the tall grasses, and apparently this dragonfly also finds the atmosphere of Drag Lake convivial. The Calico Pennant is not uncommon at other wetland habitats in south-central Hastings County, but in the coming summer months uncountable numbers of these colorful little skimmers can be found flying at Drag Lake.

The Belted Whiteface (Leucorrhinia proxima) and the Frosted Whiteface (Leucorrhinia frigida) are another pair of dragonflies that can be tough to distinguish at a glance. They are very similar in size, coloration and patterning, and both species develop pruinosity on the first few abdominal segments.

This Belted Whiteface was captured near a marsh a couple of kilometers east of Drag Lake, and examination of the hamules (top) and claspers (bottom) is the best means of distinguishing it from the Frosted Whiteface.

Dragons in the Shadows

Like most of its Baskettail and Emerald cousins (family Corduliidae) the Stygian Shadowdragon is a medium sized dragonfly about 50 mm in length. In contrast to its sun-loving relatives and odonates in general this dragonfly is crepuscular, coming out to forage over fast-flowing water at dusk and flying into the early hours of the evening.

Due to its nature the Stygian Shadowdragon is seldom encountered and has earned an undeserved reputation for being rare, but the numbers of exuviae found on rocks rising out of the water and bridge piers indicate otherwise. True to form this teneral male was spotted hanging out in a shady spot.

A better look at Neurocordulia yamaskanensis – needless to say the dragonfly was handled with great care. It wasn't fresh out of its larval exoskeleton, but it's not fully mature either, so it was studied for as short a time as possible to avoid damaging its relatively soft body.

This is not a boldly colored insect, with pale yellow markings on the thorax and abdomen, and an amber tint at the base of the wings, looking much like a faded Baskettail.

Lateral, oblique and ventral aspects of the terminal appendages. The Broad-Tailed Shadowdragon (Neurocordulia michaeli) would have a tiny spine on the ventral side of the cerci.

A feature that stood out immediately in the field but not mentioned in my books is that the cerci are somewhat flattened (unlike the cerci of, for instance, a Common Baskettail) and have a bit of a twist to them.

In hindsight the Stygian Shadowdragon depicted above was not the first encounter. On May 31st, 2014 during a tour of the Point southeast of town we had observed what looked like a washed-out teneral male Baskettail. I was unable to approach closely enough to capture or photograph the dragonfly, but Jason King had acquired an image and the mystery dragonfly proved to be a Stygian Shadowdragon.

Two sightings within a few days suggested the Stygian Shadowdragons were molting and transforming into adults, and this prompted a hunt for exuviae and/or emerging tenerals.

The exuviae, collected on June 03, 2014, were found approximately 2 meters from the water (that includes horizontal and vertical distance) on the pier of a bridge crossing the Moira River at Louisa Steet in Tweed, Ontario. The first sets of images are not the best, they were taken underneath the pier on a cloudy day using the flash.

Length is about 23 mm give or take.

Exuviae Number 1

Exuviae Number 2

The following day was sunny, making it possible to acquire sharper images. These macros of Exuviae Number 2 illustrate the critera used to determine that the exoskeleton once belonged to Neurocordulia yamaskanensis – the deep, rounded crenations on the labial palps ...

... rounded dorsal spines pointing backwards ...

... divergent lateral spines on S8, and lateral spines on S9 that do not extend past the cerci.

On June 05, 2014 another exuviae about 25 mm long was discovered on the pier of the old railroad (now the trans-Canada Trail) bridge spanning the Moira River, about 10 meters from the shoreline.

Identification of odonate naiads and exuviae can be tricky and isn't covered further than the family level in field guides. The exuviae were identified to species level with this Key to Larvae of Michigan Corduliidae.