An Odonate off the Beaten Track

The Slender Bluet (Enallagma traviatum) is not a particularly rare or outstandingly patterned and colored damselfly, what makes this pair of interest is the location where they were encountered and photographed.

The insects in the following four images were not captured so I did not examine the male's cerci or paraprocts, nor the female's mesostigmal plates. The following field marks are as per Page #61, Damselflies of the Northeast by Ed Lam (2004).

– Length is about the same as a Familiar Bluet (about 30 mm) but this damselfy is much less robust
– The color is a powder blue, but a distinctly paler shade than E. civile, E. ebrium, E. carunculatum, and other local bluet species
– The male's abdomen mostly black with blue rings when viewed from above
– Very narrow (virtually non-existent) black shoulder stripes
– Large eyespots connected by an occipital bar
– Prothorax with blue markings (visible in the dorsal view of the male, somewhat visible in the lateral view of the female)
– Top of male's S10 is black
– Narrow black mark on female's dorsal S8

The photos above were taken near the swimming area on the north shore of Stoco Lake in Tweed, Hastings County, Ontario. (Screen capture courtesy of Google Maps.)

However – according to the distribution map for the Slender Bluet in Ed Lam's book, as well as the maps at the MNR's Ontario Odonata Summary Atlas, this species does not range in southern Hastings County. There were some storms with high winds from the west a few days ago, so it's possible these damselflies were blown in from the southwest.

Although I'm fairly certain I've identified the damselflies correctly, I've emailed the images to an expert at the MNR and also uploaded them to BugGuide.Net ... it can't hurt to have some second opinions.

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Two days later, on July 25th, I revisited Stoco Lake to do a more thorough survey and see if there any more Slender Bluets present. I observed not one, but two mating pairs – four Slender Bluets – at the exact same tree where the first pair was encountered. And perched on the emergent vegetation about twenty-five meters further south were another five Slender Bluets ... two happy couples busy ensuring their genes were passed on to the next generation, and a solo male.

So it seems that Enallagma traviatum has established a foothold in Stoco Lake. (Have I been overlooking this species, and if so, for how long?) Since I wasn't risking injuring the only known breeding pair I decided to capture two of the insects in order to take some closeup shots. These aren't the greatest macros, but they are good enough to confirm the identity of this damselfly beyond any doubt.

A closeup of the male's head and thorax – note the large eyespots connected by an occipital bar, narrow shoulder stripes and extensive blue markings on the prothorax.

The male's terminal abdominal segments – S10 is black, and the profile of the cerci indicates this is actually sub-species Enallagma traviatum westfalli – Westfall's Slender Bluet. These relatively long appendages are visible in the field.

The female's the head and thorax are similar to the male's, with a lighter line visible along the middorsal carina.

The female's terminal abdominal segments, note the black bar on S8.

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July 26th ... yes, it appears that Enallagma traviatum westfalli is here to stay and is by no means an uncommon species in Stoco Lake.

9:55 AM – two males were observed perching on the rushes growing between the culvert and the pavillion. The images of these damselflies weren't worth keeping (out of focus due to strong winds).

10:37 AM – a tandem pair photographed about ten meters to the west of the boat ramp.

10:46 AM – back near the culvert again; two mating pairs of Slender Bluets can be seen in this photo.

A portrait of one of the mating males.

The same pair of damselflies as above ... the insects were so engrossed in mating they were oblivious to external stimuli and it seemed that even a life-threatening event couldn't "bug" them. Indeed, when I captured the pair yesterday to take the closeup shots, I only picked up the male by his wings. In theory the female could have escaped, but she couldn't take flight because her mate continued holding on tight with his claspers. Now that's what I call true love ...

Later in the day I spotted another mating pair near the culvert at 2:12 PM, and a lone female at 2:15 PM. In addition Jason King encountered and photographed a mating pair at the pier, for a total count of thirteen damselflies.

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July 27th ... 9:55 AM – one female Slender Bluet sighted between the pavilion and the culvert (photo below). A few minutes later at 10:05 AM I saw another female perching on the shrubbery near the pavilion. It's warm but overcast and windy so there isn't much odonate activity going on. Although the lighting could have been better at least I have an image of a female from a lateral oblique angle nicely showing all of the damselfly's identifying characteristics. Now to get a similar photo of a male.

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July 28th ... overcast, windy and on the cool side, but there are plenty of dragonflies and damselflies going about their business among the rushes near the culvert. I spotted two pairs of mating Slender Bluets today around 12:00 noon. Encountering so many mating couples indicates that this species is definitely breeding in the lake.

Any species has to not only reproduce, but do so in large enough numbers to outpace attrition due to – among other life-threatening hazards – predation. One is apt to find three species of spreadings at this site, the Northern Spreadwing (Lestes disjunctus disjunctus), the Swamp Spreadwing (Lestes vigilax) and the Elegant Spreadwing (Lestes inaequalis). And it appears that Enallagma and their other small damselfy cousins are the spreadwing's favoured prey. Today I observed two instances of female Elegant Spreadwings consuming Enallagma males (not Slender Bluets in these particular cases) ...

... and in the image below a female Swamp Spreadwing is eating a teneral female Eastern Forktail. And of course other large odes such as dragonflies aren't fussy about what they eat and will catch and dispatch whatever smaller odonate species they can overpower.

It appears that two of the Slender Bluets weren't victims of predation today, because at 2:22 PM, I encountered another mating pair perching on the rushes near the culvert. Life goes on ...

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July 29th ... a mixture of sun and clouds, windy and warm. Some bad news – the town's maintenance crews have mowed the rushes near the culvert where most of the Slender Bluets have been hanging out.

No real harm done – presumably the damselflies were able to evade the mower, and this is a view of the shoreline looking southeast at emergent vegetation between the pavillion and the culvert. The flora is mostly Torrey Three-square Rush mixed with some Flowering Rush, Pickerelweed and White Water Lily.

Since I hadn't checked it out for a few days I decided to re-visit the spot marked on the map where I first encountered the mating Slender Bluets (or perhaps it would be more accurate to say that the bluets encountered me).

I wasn't disappointed ... at 10:20 AM I saw a female perching on a leaf, and not far away on another leaf was a male.

10:24 AM – a satisfactory lateral oblique view of a male Slender Bluet depicting its key identifying marks. It's possible that this might be the same damselfly that I photographed sitting on the leaf a few minutes ago. However, not long after taking this photo I spotted a different male between the "first encounter" tree and the culvert; that makes for a count of three individual Slender Bluets this morning. Note the cerci, relatively long compared to other local bluet species and quite noticable in the field.

Having obtained acceptable images of a male, female and mating pair of Westfall's Slender Bluets, as a rule it would be time to move on to another topic. However, as far as I can ascertain these damselflies aren't supposed to range within about 250 km of Stoco Lake, so I'm going to keep an eye on them for a while ...

Which one is it? An Emerald Spreadwing (Lestes dryas), or an Elegant Spreadwing (Lestes inaequalis)?

My first sighting of an Emerald Spreadwing (Lestes dryas). I've likely stumbled across this damselfly many times in the past, but (like the Sedge Sprite, the Taiga Bluet and a few others) didn't know what it was until I acquired the two odonate guides referenced in earlier posts.

The metallic green color and small stocky build ... about 35mm to 40 mm long ... are correct for the species. This male is still relatively young as it isn't showing any pruinosity. The photos were taken on the Eastern Ontario Trail, near the marsh about one kilometer west of town.

Spreadwings can be challenging to identify, as colors often become obscured by pruinosity in older individuals. The claspers are blocked by vegetation in the lateral view above but I managed to get a satisfactory dorsal closeup, and they conform to the drawings in both of my field guides. Regardless of the damselfly's visible aspect, the claspers are the last word as to species; this is an Emerald Spreadwing (Lestes dryas).

Some views of a female Emerald Spreadwing. This damselfly is quite common along the trail, perching in the vegetation bordering the marsh. I've sighted several males and females, but no mating pairs as yet.

The ovipositor is visible in the lateral view but here is a bit more detail of the terminal abdominal segments.

As luck would have it I came across another metallic green spreadwing a couple of days later, perched on the emergent vegetation along the north shore of Stoco Lake near the boat ramp. At a cursory glance this damselfly looks the same as the Emerald Spreadwing in the photos above. It's a bit longer (50 to 55 mm), with a relatively slender build, and it's showing the pruinosity on the last abdominal segments and blue eyes typical of adult males. The luster of the abdomen is brassy rather than a true green. But how to be certain as to species?

I was unable to approach closely with the camera, and the following two overviews and the dorsal view of the claspers are scarcely adequate for the purpose of identification.

Fortunately I was able to capture the insect. (As a rule I dislike doing this for fear of mishandling or injuring it; even the oils from human skin can coat the wings and have a deleterious effect on the insect's ability to fly). Upon closer examination (and as the following ventral and lateral closeups show) it's clear that the paraprocts (lower claspers) are longer than the cerci (upper claspers). Again, what I'm seeing agrees with the diagrams in both field guides ... this is an Elegant Spreadwing (Lestes inaequalis), and my first encounter with this species of damselfly as well.

Whilst I had the insect in hand I took a couple more shots ...

This is a different male observed at the same location a few days later. Another good field mark for this species is the pale postocular area, visible in this picture. (I failed to take advantage of the opportunity to take a photo of this attribute while I had the other damselfly in hand.) It's obvious that the paraprocts are longer than the cerci despite the fact that the terminal segments of the abdomen are out of focus.

The Elegant Spreadwing is aptly named, as manifested by the brilliant green and lemon yellow of this mature female. At about 50 mm in length the Elegant Spreadwing is visibly larger than the Emerald Spreadwing. This female damselfly was photographed in the vegetation under the dam at the walking bridge ... interesting, since the fast waters and rock bottom of the river are quite a different habitat than the still waters and muddy bottom of the lake where the males were encountered.

The pale tibiae are more easily seen in the field than in most of the photos, but they are visible in the lateral view. Also note the pale postocular area in the closeup below.

The rim of the ovipositor is definitely dark, as illustrated in the field guides, but I cannot see the obtuse angle of the basal plate (compare this to the image of the teneral spreadwing's ovipositor below).

Now things get a little tougher. Female spreadwings can be hard to sort out and tenerals raise the level of difficulty. This teneral female, photographed at the marsh bordering the Eastern Ontario Trail, isn't showing much in the way of color. But the short body, about 40 mm long, robust build, ovipositor extending past the tip of the abdomen and habitat suggest an Emerald Spreadwing. Nevertheless, based on the foregoing information I cannot rule out a female Sweetflag Spreadwing (Lestes forcipatus).

The following photos of teneral female spreadwings were taken east of the boat ramp at Stoco Lake. Note how the damselfly often holds its wings closed in the manner of pond damselfly, and the luster of the wings. These damselflies were about 50 mm long.

Another teneral female, a bit older but her body still hasn't developed its adult colors. A female Elegant Spreadwing would show pale green at the back of the head and pale yellowish, not black, legs.

Furthermore, the ovipositor of an Elegant Spreadwing should have a dark rim. However, the basal plate is obtusely angled, which is what would be expected for this species. Due to a lack of experience I don't know what to make of this conflicting data, but pending further information I'm going to say this is a teneral female Swamp Spreadwing (Lestes vigilax), a damselfly that is common at this location.