Thursday, July 3, 2014

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.

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).

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.

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?

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.

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.

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.

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 ...

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.

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.