Thursday, October 16, 2014

October Odes

It's mid-October and the end of odonate season is drawing nigh. As a rule the only species apt to be flying this late are Autumn Meadowhawks, with the odd White-faced Meadowhawk and Spotted Spreadwing for variety. There haven't been any hard frosts as yet and October 14th proved to be sunny with unseasonably warm temperatures near 25°C; a visit to a local field and marsh produced a few surprises.

West of Tweed (44.46667°, -77.31972°) is a dry field which supports short grasses, Staghorn Sumac, Sweetfern, Rubus spp and Hawkweeds, with a scattering of Eastern Red Cedars that are home to a small colony of Juniper Hairstreaks. At approporiate times of the year it's a good place to find odonates that like to forage far from water such as Four-spotted Skimmers, Halloween Pennants and Mosaic Darners (Aeshna spp). Of course the ubiquitous Autumn Meadowhawks (Sympetrum vicinum) are still present at this habitat, this is a male ...

... and a female with its distinctive triangular ovipositor.

The three female Common Green Darners (Anax junius), however, were unexpected as most of their kind packed up and departed for more temperate climes two or three weeks ago. Shortly after the photo of the female in flight was taken the dragonfly angled sharply upward in pursuit of an Asian Lady Beetle, but on the verge of grasping it veered off and let it be. Ladybirds secrete a defensive chemical, an alkaloid called coccinellin, and the dragonfly seemed to recognize the beetle was potentially distasteful or toxic.

An even better find was a large (about 35 mm long) female Enallagma spp. This damselfly emerged fairly recently, its colors are bright and the black markings on its abdomen still have the glossy metallic sheen of youth. Study of the mesostigmal plates verified that this is a Familiar Bluet (Enallagma civile). A late flier indeed, the last local bluet (E. carunculatum) was encountered on September 24th. According to the Field Guide to The Dragonflies and Damselflies of Algonquin Provincial Park and the Surrounding Area, Enallagma civile is known to fly in early October, but this is the latest I have seen this damselfly in my area.

The habitat at 44.46889°, -77.31528° is a typical local wetland with Cattails and a variety of rushes and sedges, with the taller vegetation consisting of a few Tamarack and various small willows and alders. Two male White-faced Meadowhawks (Sympetrum obtrusum) were encountered here, they might well be the last for this year as their numbers have slowly but surely been declining with the passage of autumn. The Autumn Meadowhawks are still out in full force; about sixty were estimated to be flying with roughly equal numbers of males and females. Of course most were engaged in a frenzied last minute orgy of mating and oviposition, doing all they can to ensure their genes make it into the next generation before the onset of cold weather puts an end to their little lives ...

No female Spotted Spreadwings (Lestes congener) have been seen at this marsh during the last couple of surveys. It appears that the males can't find any either and in desperation are taking whatever they can get. Yes, that's two males in tandem in the second out-of-focus photo. The other male wasn't compliant and they separated ... some relationships are doomed to failure from the very start ...

There are still some Aeshna spp flying, not unknown in October but not common either. I didn't have a net to capture the two darners for closeup shots but they both obligingly perched or hovered long enough to be identified. One was a beautiful green form female Canada Darner (Aeshna canadensis), it could well be the same individual captured and photographed at this habitat on October 1st. An old male Lance-tipped Darner (Aeshna constricta), its colors somewhat obscured and wings whitened and frayed by age, was also doing its rounds.

All in all, not a bad count considering the location and time of year. No doubt there are a couple or three other species still hanging in there, if so photos or accounts will be posted, stay tuned ...

October 22nd – time, as it has a way of doing, has passed and is now moving toward late October. Today was sunny and breezy with the temperature hovering around 10°C, and there were over twenty male and seven female Autumn Meadowhawks (all seven females were in tandem) and a lone female White-faced Meadowhawk flying at the marsh. As might be expected the White-faced Meadowhawk was an old girl with dulled colors and frayed wings.

Despite not having observed any for the past couple of weeks, there are still some female Spotted Spreadwings around, in fact three of them, as well as four males.

Last but not least, one Aeshna spp was hawking insects along the trail but it was too far away for me to make out any details and ascertain the species. And it seems that the late flying dragonflies and damselflies may be with us a little bit longer. There's no frost in the forecast for at least a week and next Tuesday the temperature will be a balmy 17°C.

Thursday, September 25, 2014

An Equinoctial Odonate

Perhaps post-equinoctial would be more appropriate, as this immature male Twelve-spotted Skimmer (Libellula pulchella) was encountered on September 24th, 2014 at the Tweed Fairgrounds (south-central Hastings County, Ontario).

The Twelve-spotted Skimmer is a summer dragonfly, the first local fliers were observed at the Vanderwater Conservation Area in mid-June, a couple of very old males on their last legs were sighted as recently as ten days ago. But this is a young dragonfly, as yet lacking the pruinescence on the abdomen typical of fully mature males, and to see one flying this late in the year – the second day of autumn – is unusual to say the least.

Striking Spiders

Striking – arresting the attention and producing a vivid impression on the sight or the mind, attracting attention by reason of being unusual, extreme, or prominent, conspicuously attractive or impressive.

A dazzling Dark Fishing Spider, arresting the attention of an observer by virtue of her size, from the cephalothorax to the tip of the abdomen she is a mere 20 mm in length. Dolomedes tenebrosus can attain a body size of up to 26 mm with the legs spanning 90 mm but this one is deflated after laying her eggs. Like most Pisauridae (a.k.a. Nursery Web Spiders) she stands guard over her brood until they a bit older and better able to fend for themselves.

The spiderlings have already been through one molt and the pale exuviae can be seen littering the nursery.

A couple of closeups of the female, with one of her offspring clinging to her abdomen in the second photo.

A friend brought this wondrous Wolf Spider to me for identification, but unfortunately for the spider it was DOA when it arrived. The body length of this particular female Tigrosa aspersa was 23 mm and the legs measured 70 mm across, however, these "wolfies" can reach a respectable 30 mm.

The spider did indeed produce a vivid impression on the sight and the mind – the person who killed it woke up in the night and found the spider crawling on them; I wasn't informed what part of their anatomy. They immediately dispatched it (this was not the intent or one of the definitions of "striking" in the title), but under the circumstances it's pretty hard to fault a person for being startled ...

The arrangements spider's eyes are unique to each family, and this one's eye pattern is typical of the family Lycosidae.

A marvelous Marbled Orbweaver, in my opinion this is by far the most beautifully colored and patterned spider I have ever encountered. Araneus marmoreus is small compared to the foregoing two spiders, the body measures about 20 mm and the legs are relatively short, but it makes up visually what it lacks in sheer bulk – conspicuously attractive or impressive indeed!

The Marbled Orbweaver featured above is a female, and she's gravid and ready to lay her eggs any day to start the life cycle of her kind anew. On the other hand the female Longjawed Orbweaver (Tetragnatha spp) in the following photo won't likely get her chance to pass her genes on to the next generation, that opportunity now belongs to the small wasp, only about 3 mm in length, that's clinging to the underside of the spider.

The image was acquired under poor lighting conditions and is a bit out of focus but the wasp's ovipositor, ready to deliver its egg (or eggs?), is clearly visible in the photo. It's interesting to note that the wasp is in a "safe zone" and the hapless spider cannot reach it with its jaws.

The picture has been uploaded to BugGuide.Net where hopefully someone can identify the wasp. As of now I have no idea as to the wasp's species (Ichneumon, perhaps?) or life cycle – does it lay one egg per spider, or more? Will the spider be paralyzed by the hymenopteran's venom, or will it continue to go through the motions as the wasp larva (or larvae?) consume it from within? Whatever the story may be, like everything else in the world of nature we can be certain it's fascinating and compelling, possibly even (from our human viewpoint) bizarre ... which are all synonyms for the word "striking".

Wednesday, September 24, 2014

A female Saffron-winged Meadowhawk

East of Tweed, near a patch of wildflowers along Lakeview Lane (44.478429°, -77.301881°) – my third sighting of a Saffron-winged Meadowhawk this year (the other two were at Dry Lake, south of Marlbank). Sympetrum costiferum is larger – this individual measured 38 mm – and darker than the average Sympetrum apt to be encountered in our area, and it has a habit of perching on the ground.

As with other Sympetrum, the female Saffron-winged Meadowhawks is orange (compare to the red abdomen and brown thorax of the male).

The veins along the leading edges of the wings are saffron colored and the pterostigmata are long and pale orange.

Closeups of the face ...

... and its genital plate, a part of the dragonfly's anatomy that is unique and distinctive for each species.

Saturday, September 20, 2014

Amethyst Aster (Aster x amethystinus)

A hybrid between two very different looking species, the New England Aster (Symphyotrichum novae-angliae) and the Heath Aster (Symphyotrichum ericoides), the Amethyst Aster (Aster x amethystinus) exhibits characteristics of both parent plants which, not surprisingly, were abundant in the high and dry field where the Amethyst Asters were encountered.

The following groups of three photos illustrate the features of the Amethyst Aster, New England Aster and the Heath Aster respectively.

The overall aspects of the plants.

The blossoms resemble those of the New England Aster but are only about half as large and bear fewer ligulate flowers.

Even the involucral bracts or phyllaries are intermediate between those of the progenitor species.

More studies of the Amethyst Aster – the relatively small leaves are crowded and clasp the stem.

The main stem of the plant is hairy.

Wednesday, September 17, 2014

A Late Season Common Whitetail

Encountered west of Tweed near a marsh bordering the trans-Canada Trail (44.46889°, -77.31528°) – a surprising find as the final few surviving Common Whitetails (Plathemis lydia) were flying nearly a month ago, and no others have been sighted until now. The last sighting in this area was a male on August 18, 2014 near the intersection of River St. and the trans-Canada Trail (44.473668°, -77.312911°).

The dulled colors aside, this female is in really good condition with no wear and tear on the wings, it was extremely wary and alert and it sure could fly. Half an hour of patient stalking were required to capture the agile odonate.

As of today – September 17th, 2104 – the dragonfly is still alive and well. Sad to say, her days are numbered. Even if she manages to evade the Darners patrolling the marsh (six species currently known – and lots of them!) the first frost of autumn lies in the not too distant future ...

Adult dragonflies can live for a few weeks if they don't fall victim to predators or the elements. Looking at the lackluster colors of the eyes and thorax and the frayed wings of this male Common Green Darner (Anax junius), one can only wonder how old it might be.

An superannuated female Lance-tipped Darner (Aeshna constricta). Again, the coloration and patterning – originally a beautiful yellow-green – is obscured, the cerci are broken, and the wings have obviously seen their fair share of use and abuse.

The colors of this male Canada Darner's (Aeshna canadensis) are fairly bright and only the whitish discoloration and ragged edges of the wings suggest its age.

The dragonfly's face, however, was something of a shock – the brown clypeus is hardly typical of this species. Discoloration of the exoskeleton due to old age? Or an aberrantly colored individual?

Tuesday, September 16, 2014

Lake Darner (Aeshna eremita)

At first glance the Lake Darner looks very similar to the Canada Darner. The main distinguishing characteristics are the distinct dark cross-stripe on the face, the very deeply notched anterior thoracic stripe and a second thoracic stripe that is relatively broad compared to other Aeshna species.

On the average Lake Darners are larger than Canada Darners; this male measured 75 mm in length. In addition the cerci of Aeshna eremita are strongly bent upward and bear prominent bumps on the upper surface, but without a Canada Darner handy to compare these features to the differences were not obvious in the field.

A female Lake Darner, at 72 mm almost as long as the male encountered on September 15th. The field marks are right on the money and identical to those of the male, with a notched (the notch being nearly semi-circular) first thoracic stripe and wide second thoracic stripe ...

... a central line on S2 joining the band on S1, and fused blue spots on S10 (the male deviated on this feature, his were touching, but just barely).

A closeup of the face depicting the cross-stripe.

The terminal appendages (cerci) are rounded at their tips and similar to those of the female Canada Darner. Again, note the fused blue spots on S10.

Details of the genital plate and styli, however, these features aren't useful for separating this darner from other related species (at any rate, they are not mentioned in field guides).

The Lake Darners encountered thus far have been unbelievably tame. The female had captured an insect and, looking for a place to sit and eat it in peace, tried perching on my face twice. A male (perhaps attracted to the female?) stopped to perch in the tall grass within arm's reach as the female was being photographed.