The Slender Bluets of Stoco Lake

In late July of 2013 some Slender Bluets were found to be breeding in Stoco Lake, located in south-central Hastings County. As of that time Enallagma traviatum was only known from southwestern Ontario. The past winter was the harshest in the last twenty years, did the little colony of damselflies survive?

Slender Bluets begin to fly about mid June in the more northern parts of their known range, so late June seemed like a good time to begin looking for them locally. The first 2014 encounter at Stoco Lake occurred on June 26th, and although the photo is out of focus the following features are quite obvious:

– Large blue eyespots
– Lots of blue on the prothorax
– Very narrow shoulder stripe
– Abdomen very thin, mostly black, S8 and S9 blue, S10 black
– Long terminal appendages

June 29, 2014: between 7:30 AM and 8:00 AM – over twenty males and two tandem and/or mating pairs were sighted. The Slender Bluets weren't particularly wary but they were still difficult to photograph because they wouldn't sit still. The males were continuously harassing one another and engaging in territorial combats over a choice leaf. The damselflies were concentrated in two Silver Maples near the shoreline, perching at about eye level or a bit higher. Based on their appearance they have likely been flying for at least a week to ten days.

Judging by their numbers it appears that the Slender Bluets not only survived but are thriving. Perhaps this is not unexpected since they have been recorded at the same latitude from Wisonsin and Michigan. A few images of one of the males, looking at the terminal appendages this is clearly Enallagma traviatum westfalli.

One of the two tandem/mating pairs encountered.

Images of three different males perching in the trees.

Male #1

Male #2

Male #3

June 30, 2014: between 10:00 AM and 10:30 AM – three tandem and/or mating pairs were observed, one of them to the west of the pier. Some photos of a male and two of the pairs, again, it was difficult to find a male actually sitting still. For reasons known only to Slender Bluets some leaves were better than others, and there was a constant power struggle for the best spot.

July 01, 2014: between 8:00 AM and 8:30 AM – still lots of males in the trees, and another two tandem and/or mating pairs were observed. Note the distinctive black mark on female's S8.

Slender Bluets prefer ponds or lakes with plenty of emergent vegetation and treed shorelines, and Stoco Lake fits that description perfectly. These hardy little damselflies have demonstrated they can withstand the rigors of a serious winter and the local predators, and there are definitely more of them than there were last summer – how extensively have they populated the lake, anyway?

It seems that Enallagma traviatum westfalli is no longer a "colonist" but rather a permanent resident and here to stay.

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July 04, 2014: about 9:00 AM – over ten male, and one tandem pair, of Slender Bluets were sighted in the rushes and shrubs along the lakeshore. This does not include the usual crowd hanging out in the trees (they have already been counted recently).

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July 09, 2014: east of Tweed, along the trans-Canada Trail (44.480417°, -77.301251°) – one male and one female Slender Bluet were perching on the shrubs bordering the trail; this is a fair distance from water and the first encounter not at Stoco Lake.

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July 11, 2014: east of Tweed, near intersection of Lajoie Rd. and the trans-Canada Trail (44.48250°, -77.29556°), a wooded area with clearings supporting wildflowers – 2 males, a good distance from Stoco Lake, the lagoon, however, is not far away, perhaps the damselflies are breeding in there?

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July 12, 2014: two areas along the north shore of the lake, east of Tweed, were surveyed. Both habitats are similar to where the Slender Bluets are currently present, deciduous woodlands to the north, and the lake – supporting pondweed, water lilies and some emergent vegetation – lies to the south.

44.478348°, -77.299506° – east of the mouth of the Moira River and south of Lakeview Lane.

44.479706°, -77.297234° – a gneiss outcrop on the north shore of Stoco Lake.

There was no evidence of Slender Bluets flying at either of these sites.

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July 16, 2014: north shore of Stoco Lake – east of the boat pier (44.474563°, -77.306227°) at about 8:30 AM – two males, in the same tree where a couple of weeks ago there were at least twenty. It appears that the Slender Bluets have had their day in the sun for this year.

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July 19, 2014: trans-Canada Trail east of Tweed – deciduous woodland with clearings created by the trans-Canada Trail, Stoco Lake is nearby to the south (44.489945°, -77.288357°). A lone male Slender Bluet was encountered perching on the Poison Ivy along the side of the trail.

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August 03, 2014: north shore of Stoco Lake – east of the boat pier (44.474563°, -77.306227°) at about 9:00 AM. It was warm but overcast, and though otherwise there was not much odonate activity two male Slender Bluets were sighted perching in the Silver Maples along the shoreline. I haven't encountered any of these damselflies for a couple of weeks and am surprised they are still flying. One of the insects was captured in order to take photos of the head and thorax, and the claspers.

Slender Bluet male #1 ...

Slender Bluet male #2 ...

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August 19, 2014: near the Pavilion – (44.472550°, -77.307777°) shortly after 12:00 noon, the weather was warm and sunny. The habitat is the same as near the boat pier where the majority of these damselflies were encountered earlier this summer ... mud bottom and a marshy shoreline with relatively shallow stagnant water supporting emergent plants such as rushes, water lilies, wapato and pickerelweed.

Over thirty Tule Bluets were foraging for food or searching for a mate among the shoreline rushes, and this female Slender Bluet (as well as a lone male Hagen's Bluet) stood out like a sore thumb among the larger, darker Tule Bluets. It looks like it's anyone's guess how late in the season these damselflies are going to be flying, last year they were none to be found after late July. According to Ed Lam's "Damselflies of the Northeast" Slender Bluets fly until early September in New Jersey, but that's a long way from Stoco Lake in south-central Hastings County, Ontario!

Closeup shots of the head, thorax and terminal abdominal segments.

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September 10, 2014: north shore of Stoco Lake – east of the boat pier (44.474563°, -77.306227°), at about 2:00 PM, cloudy, possibly rain on the horizon and very breezy. It's no longer a matter of guesswork whether or not the local Slender Bluets fly in September.

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Northern Bluet (Enallagma annexum)

Formerly known as Enallagma cyathigerum and its range believed to to be circumpolar, recent research indicates that the North American and Eurasian lines of this bluet diverged 250,000 years ago and the North American stock now goes by the epithet Enallagma annexum.

Northern and Boreal Bluets cannot be reliably distinguished in the field by sight and it's necessary to examine the male's terminal appendages or the females mesostigmal plates. A tandem pair of Northern/Boreal Bluets – both species have large postocular spots and tapering humeral (shoulder) stripes.

A dorsal view of a typical Northern/Boreal Bluet female – the paired blue spots on S8 may be fused in some individuals. The females can be either blue or tan.

The cerci of the male Northern Bluet are sharply upturned at their lower tips.

Terminal appendages of the Boreal Bluet – the cerci are rounded and angled downward.

The Vernal Bluet (Enallagma vernale) must also be examined in the hand to separate it from the Northern Bluet, the cerci of the male Vernal Bluet have a ridge. There's no way my camera will pick up that kind of detail but it should be visible with a 20× loupe, and thus far I have found no evidence of Vernal Bluets flying in my area.

As of this writing I'm uncertain whether the Vernal Bluet is considered a subspecies of the Northern Bluet (according to my field guide there is evidence of hybridization) or has been elevated to species level.

A Few Notes on Water Nymphs

It's inevitable that the "bugs" which generally pique the interest of most people are the adult form of the insect. The colorfully patterned wings of a butterfly or the iridescent elytra of a beetle that catch our eyes do so because in many cases insects are flying around trying to attract attention – that of a potential mate. The colors might be aposematic, bright, bold and arranged in striking patterns, a warning saying "don't mess with me". Or as often as not, an insect gets noticed because it's just plain weird and bizarre, it's so different that it almost qualifies as an alien form of life.

Ditto for dragonflies and damselflies – they're generally large or colorful, and pretty hard to miss on a visit to a river, lake or wetland. But the reality is that the odonates we see flying around are actually near the ends of their lives, on average lasting for only a couple of weeks before succumbing to predation or bad weather. Larger dragonflies such as darners can spend two or three years in their larval state, and by focusing only on the adult insects one is missing out on understanding most of their life cycles and roles in nature.

The following notes and photographs, not to mention the rest of this blog, are the work of a beginner who has taken only the first few steps down the long and never-ending road of learning. If you've had a close encounter with a cool naiad that's new to you and you're looking for a definitive answer as to species you've come to the wrong place, instead, try one of the links to the keys for identifying odonate larva further down this page.

Damselfly naiads are generally smaller than dragonfly larvae and have three external gills at the tips of their longer, slimmer abdomens. This is the larva of a Pond Damselfly, family Coenagrionidae.

The naiads of family Lestidae tend to be larger. Based on the habitat where it was found – a vegetated marsh – this could be a Northern Spreadwing (Lestes disjunctus), Sweetflag Spreadwing (Lestes forcipatus), Slender Spreadwing (Lestes rectangularis) or Amber-winged Spreadwing (Lestes eurinus).

The riparian habitat and very long basal segments of this naiad's antennae indicate family Calopterygidae. There are two possibilities locally – the Ebony Jewelwing (Calopteryx maculata) and the less commonly encountered River Jewelwing (Calopteryx aequabilis). According to Odonata Larvae of Michigan – Key to the Calopteryx Larvae of Michigan ~ "... tubercles behind eyes prominent and acute ..." ~ looking at the oblique views the spine behind the eye is clearly prominent and acute. This is the aquatic avatar of Calopteryx maculata.

Dragonfly naiads are stouter and more robust than their damselfly cousins, and their gills are internal (in other words, they breathe through their asses). This is a typical dragonfly larva, and based the adults of the species observed at the heavily vegetated lakeshore habitat and the naiad's profile it's a Skimmer, family Libellulidae.

Dozens of exuviae can be found during the summer months at the same lakeshore habitat. It's often advantageous to study exuviae as opposed to larvae since they can be examined and photographed without fear of hurting or killing the insect. Based on their general outlines these are Libellulidae exuviae, probably one of the common larger species such as the Widow Skimmer (Libellula luctuosa), Halloween Pennant (Celithemis eponina), Eastern Pondhawk (Erythemis simplicicollis) or Blue Dasher (Pachydiplax longipennis).

Celithemis eponina ~ can be ruled out, its eyes taper to conical points.
Pachydiplax longipennis ~ lacks the prominent dorsal spines.
Erythemis simplicicollis ~ "... lateral spines absent ..."
Libellula luctuosa ~ best guess, but most of the information needed for an exact ID is not in the photo. Next year I'll try to keep an eye out for emerging adult dragonflies, and it shouldn't be too difficult to capture the exuviae.

Identification to the species level might be difficult, but dragonfly naiads and exuviae can be narrowed down to as to family based on their general shape. This relatively stout exuviae is another example of family Libellulidae, and according to the Odonata Larvae of Michigan – Meadowhawks it keys out as a Ruby Meadowhawk (Sympetrum rubicundulum).

The best means of being certain as to the identity of an exuviae is to observe the eclosion or emergence of the adult dragonfly. This exuviae was left ehind by a Whitface – Leucorrhinia spp. – probably a Frosted Whiteface (L. frigida) as it's by far the most common of the Leucorrhinia species observed at the marsh where the exuviae was collected.

And about an hour and twenty minutes before it was photographed, this cast-off exoskeleton was worn by a female Four-spotted Skimmer (Libellula quadrimaculata).

Early last month I posted images of some family Cordulegastridae naiads. The shape of the naiads is distinctive and unmistakeable, but I have yet to encounter adults of this species (whichever one it may be!) and without having discovered the naiads would have no idea they were in the area – a great example of why the study of the naiads and exuviae is worthwhile.

And three years ago I uploaded a sequence of photos (taken by Pauline Campbell) of a Dragonhunter making its final molt to adulthood. In this case the profile of the exuviae is not typical of most Gomphidae, the burrowing larvae of Clubtails tend to be somewhat slender rather than broad and leaf-like.

Cruiser naiads are long-legged and spidery in appearance. There are two possibilities in this area – the Swift River Cruiser (Macromia illinoiensis), and the more commonly encountered Stream Cruiser (Didymops transversa). Due to the limits of the camera's macro (Canon PowerShot A530) and lack of experience in knowing what characteristics to photograph and/or observe when in the field I was unable to resolve the identity of the naiad to the species level ~ Aquatic Insects of Michigan – Macromiidae - Cruisers.

However, the experts at BugGuide.Net identified this Cruiser naiad right down to the sub-species level (perhaps based on the length of the lateral spines on S9?). Depending on which book or authority you want to follow, it's a Swift River Cruiser a.k.a. Illinois River Cruiser.

You've got to love that cute little frog-like face ...

After the photo session the naiad was released. The insect's colors are much more vibrant in its natural setting, however, underwater photography introduces greens and blues reflected from the sky and water.

Darner naiads and exuviae have relatively large eyes, and long but robust abdomens. By studying the images of the prementum, labial palps and blades posted at BugGuide.Net, I was able to ID this exuviae as belonging to a Canada Darner (Aeshna canadensis).

There were about a dozen of these dark exuviae clinging to a bridge over the fast moving water of the Moira River. Three of the images below are of an exuviae that belonged to a female – note the ovipositor.

BugGuide.Net to the rescue again ... the cast-off exoskeletons were left behind by Fawn Darners (Boyeria vinosa). I should have figured, both by the general aspect of the exuviae and because I was starting to see adults flying.

Thus endeth this lesson in how little I know ... and there's still a long way to go ...