Male Arrowhead Spiketail – trans-Canada Trail

East of Tweed along the trans-Canada Trail are three sand-bottomed woodland streams that are known to support Spiketails. There's a fourth habitat that looks eminently suitable but it hasn't been investigated as yet.

In early June of 2011 a female Arrowhead Spiketail was photographed near Alexander Street. Last August, Cordulegaster naiads – and plenty of them! – were discovered inhabiting another stream (they were still doing all right in mid-January). And earlier this spring naiads were found in a creek near the intersection of Sulphide Road and the trans-Canada Trail.

Studies of the larvae proved inconclusive as to whether they might be Arrowhead Spiketails (Cordulegaster obliqua) or Twin-spotted Spiketail (Cordulegaster maculata) but a couple of days ago Mother Nature gave a hint as to which species it might be ...

Of course, this doesn't rule out the possibilty that Twin-spotted Spiketails might be co-habiting with their cousins.

Another Stream full of Spiketails!

It seems like in another month to six weeks I'm going to have to be in two places at once. Just west of the intersection of the Sulphide Road and the trans-Canada Trail is a woodland steam with a sandy bottom.

Ideal Spiketail breeding habitat, it definitely looked like it was worth checking out, and sure enough there was a female Spiketail naiad in my second handful sand. She's about 40 mm in length and should emerge for her final molt to adulthood in a few weeks.

Needless to say these naiads they are impossible to spot when they are in full stealth mode, buried with only their eyes exposed.

The Spiketails are also doing well in the stream where I first encountered them. There's a lot more happening now than back in the middle of January.

It didn't take much effort to dredge up a couple more female naiads, one about 25 mm long and the other 45 mm.

Late last autumn my efforts to ascertain the species proved inconclusive, though I was able to narrow the possibilities down to either the Arrowhead Spiketail (Cordulegaster obliqua) or the Twin-spotted Spiketail (Cordulegaster maculata), with what little data I had weighted in favor the latter. Rather than trying to monitor two streams separated by almost two kilometers, in another couple of weeks or so I'm going to capture a couple or three larvae and try to raise them.

It's been ten months since I first discovering the naiads, with some luck and a little more patience I'm going to find out what they are soon ...

Close Encounters with Dragonflies in mid-January

The New Year started off with some serious winter weather, but Mother Nature has given us a break for the past three days, with the temperatures hovering around a more bearable 5°C, plus or minus a degree or two. As good a time as any to take advantage of the moderate meteorologic conditions and search for whatever dragonflies might be out and about.

The woodland stream depicted in the next photos is along the trans-Canada Trail, roughly half a kilometer east of Tweed. This is the view looking north of the trail.

And it didn't take long to find a dragonfly. She is 30 mm in length, and it definitely is a girl – the tiny ovipositor can be seen peeking out between abdominal segments eight and nine.

A photo of the stream to the south of the trail, and again, a few scoops of sand and silt from the stream bed produced a pair young males. The larger of the two is 25 mm long, the other little guy is 18 mm in length.

This is the same site where I found the Spiketail naiads last August, and I know there are lots of them lurking in the bottom of the stream. The real purpose of this excursion was not to look for dragonfly naiads, it was to satisfy my curiosity as to what they might be eating. Are any of these insect species food for Cordulegaster larvae? I don't know for certain, but given what I've read about odonate larvae in general, they are voracious eaters and will take whatever they can capture and overpower.

There are some mayfly naiads inhabiting the stream but they are not common. Caddisflies are a bit better represented, I found two species, a small one that makes its protective casing out of grains of sand, and the larva in the following photo. (Incidentally, the insect was pulled from its case by accident, I didn't tear it out for the sake of a few pictures.)

I think the caddisfly larva is probaly genus Triaenodes, at any rate both the insect and its casing strongly resemble the one in the next photos (taken during the much warmer days of a summer long past).

There were also some stonefly naiads hiding in the leaf debris along the steam's edge. Like the mayflies, they are not common, and they are tiny, almost translucent, only about 5 mm long. Not much of a meal for the naiads that I dredged up, but good enough to feed a hatchling.

The most likely source of nourishment for the growing young Spiketails are the large, maggot-like critters in the following images. Based on their aforesaid "maggot-like" aspect, I surmised (as it turned out, correctly) that they might be cranefly larvae, indeed, I think they are the larvae of the Giant Crane Fly (Tipula abdominalis). The stream bed is teeming with these detritivores and one scoop of muck can yield half a dozen. They are large, normally chunky, oval shaped and grub-like in appearance and about 25 mm long, but can extend themselves to 40 mm or 60 mm.

The insects didn't like being out of their element and weren't co-operating, so this is best macro I could obtain of the spiracular lobes. Here's a link to some much better images at BugGuide.Net.

This is an old photo from a few years ago of the adult fly, not an uncommon species, and aptly named too.

The air was warm enough to permit some active insect life outside the insulating confines of the water and there were a few small black midges flying around. And before I left for home I saw this on the snow ...

A little Long-jawed Orbweaver spiderling, no longer than 3 mm. No matter how tough the circumstances or adverse the conditions, life goes on ...

Spiketail Naiads

Found buried in a sand-bottomed stream flowing through a wooded area, 25 mm in length, it's definitely Cordulegaster spp. – but which one?

There are three members the family Cordulegastridae in our area: the Delta-spotted Spiketail (Cordulegaster diastatops), the Twin-spotted Spiketail (Cordulegaster maculata), and the Arrowhead Spiketail (Cordulegaster obliqua). According to the Ontario Odonata Summary Atlas the Arrowhead Spiketail is by all accounts an uncommon dragonfly and it's tempting to rule it out on this basis. But by the same token the naiad was encountered in appropriate habitat within half a kilometer of where an adult female Cordulegaster obliqua was sighted and photographed in mid-June of 2011.

The next picture was taken indoors using the flash ... not much of an improvement, but a friend with a better camera has taken some cleaner, more detailed images under brighter lighting. The photos in this post have been submitted to BugGuide.Net, and maybe someone who has experience with identifying odonate naiads can take this to the species level. (EDIT ... one of the forum members has posted a Key to the Michigan Species of Cordulegaster, and it doesn't look like these images are going to be good enough ...)

The youngster ate two mosquito larvae while in captivity, and upon being returned to the stream where it was found it quickly proceeded to bury itself in the sand and silt. Spiketail larvae hunt by concealing themselves under the sediment and leaving only their eyes exposed, lurking in ambush for an unwary passerby. Hopefully it will survive the hurdles of larval life long enough to attain maturity, and who knows, we may meet again and it can pose for more photos next summer ...

Where there's one Spiketail naiad it's reasonable to expect there might be others, so it looks like more forays to the woodland stream in the near future to acquire a larger, older instar to study.

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The story continues ... upon visting a stretch of the woodland stream between the trans-Canada Trail and Lakeview Lane, a little south of the site of yesterday's find, I discovered that it's virtually crawling with Spiketail larvae! Within a distance of no more than three meters I found four naiads between 15 and 18 mm in length, one the same size as the previous day's find (25 mm), and four at 35 mm. (I should have saved all of the naiads and done a group shot.)

If they survive that long, three of these will emerge and transform into adults next year, and one, the first of today's finds, will not, as it was dead when I came upon it. Bad luck for the naiad, but this gave me an opportunity to photograph the prementum and palps on a relatively large specimen. Here are the images in the order they were acquired, and it's only fair to point out that this isn't really good science, as the characteristics we're looking at in the following images are not attributes of the same individual.

The best available macros of the outer surface of the serrated palps, the palpal setae and the premental setae. There are six palpal setae – although only five hairs are visible in the image there are six "roots" and the other palp has six as well (not visible due to the angle the photo). There appear to be ten, not more than eleven, premental setae. Unfortunately, being new to this, I neglected to acquire an image of the epaulet.

One of the smaller – 15 to 18 mm – naiads.

Another large (35 mm) – but alive – individual. Since I didn't have a ruler to determine the length of the insects I used a stick or my spare key, which were measured after I went home.

The frontal shelf (the part of the head between the antennae) is rounded in dorsal view. Another error in judgement due to inexperience ... while in the field I never thought to photograph or at least examine the frontal shelf's lateral aspect on any of the naiads.

A ventral view ... scaling the prementum as best I can on the computer screen, the palpal width is at least 2.5× the basal width.

A couple of views of the abdomen. The lateral spine of S8 does not appear to be strongly upcurved, in fact, I can't really see any lateral spines, just hair ....

The Spiketail naiad in its habitat upon being released, out of focus since it's both underwater and in motion. Being submerged brings forth a lot subtle, beautiful colors that completely disappear when the insects are removed from their natural element.

Knowing the length of a female naiad's developing ovipositor in relation to S9 would be helpful, but all of the specimens examined today, save the naiad in the next collection of images, were either too young to have developed an ovipositor or were males. This individual was also 35 mm in length and doesn't appear any different from the other naiads examined thus far ... except ... look carefully at the lateral views of the abdomen.

There's no evidence of an upcurved lateral spine on S8.

Jackpot! This one's a girl and the ovipositor is clearly a little longer than S9.

A few pictures of the larva after it was set free to go on its way, again, there's a striking difference in appearance compared to when it was perching on the palm of my hand. As with the other naiads captured, I didn't take any photos of the mouth parts and associated setae, as I didn't feel I could accomplish this without injuring the insects.

Assuming the naiads are all the same species and share all of the above characteristics (no, this definitely isn't exemplary science), and looking at that Key to the Michigan Species of Cordulegaster, it's safe to rule out the Delta-spotted Spiketail (Cordulegaster diastatops). There do appear to be six palpal setae, or the roots thereof if not the actual setae, but I do not count more than eleven premental setae. And – the ovipositor of the female is definitely longer than S9.

So it's still a bit of an open question because of inconsistencies in the number of palpal setae, but for now the weight of the evidence points toward the Twin-spotted Spiketail (Cordulegaster maculata). Despite the numbers of larvae, and although this species does range in this area, I have never encounterd it in its adult incarnation. But next summer I will certainly be staking out this stream when the Twin-spotted Spiketails are expected to emerge and fly in early June.

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August 12th ... checking out a section of the stream to the north of the trans-Canada Trail turned up half a dozen naiads. Four larvae were between 15 and 20 mm in length, and another two larger specimens measured 30 to 35 mm long. This makes for a grand total of sixteen in a fairly short stretch of water, so the Spiketails are hardly uncommon. Yet I have only encountered one adult in five years!?