An anomalous male Eastern Forktail, and how to distinguish a disorderly disarray of damselflies

By far the most common local species, I've likely seen thousands of these small damselflies but to date this is the only Ischnura verticalis I've observed exhibiting a discontinuous antehumeral stripe.

Two days later I stumbled across another Eastern Forktail with a pinched or reduced shoulder stripe.

An imposter that might be mistaken for an Eastern Forktail: there were about a dozen of these small damselflies (about 30 mm long) in the tall grasses just under the dam shortly before sunset.

Note the vulvar spine on S8 ... definitely an Enallagma female.

The dorsal view is not the best due to the poor lighting. But the central blue oval spot on S9 is diagnostic, as are the small blue ocular spots, the narrow yellowish antehumeral stripe and heavy black humeral stripe, the pale yellow on the legs and the orange pterostigmata. This damselfly is a female Rainbow Bluet (Enallagma antennatum). I'm looking forward to photographing the males ... but where are they? Only the females were out and about ...

This damselfly is a teneral male Eastern Forktail ...

... and the next two images depict a teneral male Eastern Forktail with a broken (virtually nonexistent) shoulder stripe. Now have a look at the lateral view of a male Rainbow Bluet (Enallagma antennatum). The red tinted eyes of the teneral Eastern Forktail may be deceptive but (aside from the shoulder stripes) the ocular spots and the patterns on the terminal abdominal segments are quite different.

A male Fragile Forktail (Ischnura posita) has an "exclamtion mark" shaped shoulder stripe. This damselfly is also generally smaller than the Eastern Forktail and the last abdominal segments of this species are never blue.

Although they look similar at first glance mature female Fragile Forktails and Eastern Forktails can also be distinguished by their shoulder stripes. The shoulder stripe is broken in the mature female Fragile Forktail shown below, but solid in the mature female Eastern Forktail.

The following two immature female Ischnura posita haven't developed the pruinosity typical of the older females. Note the pale blue of the broken shoulder stripes and the sides of the thorax.

Thus far I have only encountered blue Fragile Forktail females in this area but according to the books they can be tan or grey. The females below were photographed at the marsh bordering the Eastern Ontario Trail, where this insect is abundant and not likely to be added to the endangered species list any time soon. Another good habitat to seek out these tiny damselflies are the placid pools of water hedged by low, dense vegetation along the Moira River. Now and again I've found the odd stray foraging in flower gardens a fair distance from the nearest water.

Fragile Forktail (Ischnura posita)

At 25 mm long this is our smallest local damselfly. While this species doesn't seem to be as common as the Eastern Forktail it's well worth seeing, the males look like little jewels as they flit through the foliage.

Its smaller size, the "exclamation mark" shoulder stripe, and lack of blue on the end of the abdomen distinguish the male Fragile Forktail from the Eastern Forktail.

Not sure what kind of behaviour this is ... perhaps the damselfly equivalent of obelisking?

A Few Photos of some Common Damselflies

Most of the damselflies and dragonflies in this blog were identified with the help of the Field Guide to The Dragonflies and Damselflies of Algonquin Provincial Park and the Surrounding Area. This book is a must have reference for the serious naturalist. It covers the Odonata apt to be found in southern Ontario and the illustrations and species accounts are excellent.

The first group of pictures are Pond Damselflies, family (Coenagrionidae).

Violet Dancer (Argia fumipennis violacea), males and female. It's impossible to mistake the males for any other local species.

Powdered Dancer (Argia moesta), male

Stream Bluet (Enallagma exsulans), male, and a mating pair

Skimming Bluet (Enallagma geminatum), males and females

A couple of shots of a male Tule Bluet (Enallagma carunculatum) ...

... and a female Tule Bluet

Tule Bluets mating, in the second photo the pair are just disengaging from the "wheel" or "heart" position.

... and a male Familiar Bluet (Enallagma civile)

The ubiquitous Eastern Forktail (Ischnura verticalis) ... male, immature female, mature female and a mating pair

Fragile Forktail (Ischnura posita), male

A male Slender Spreadwing (Lestes rectangularis); the long, thin abdomen and lack of pruinosity on the last segments are diagnostic. This damselfly is a member of the family Lestidae, the Spread-wing damselflies, which typically hold their wings at about 45° to their body rather than folded together in the manner of pond damsels.

Without a clear photo or study of the male's claspers I stuck my neck out and originally misidentified the following specimen as a Northern Spreadwing (Lestes disjunctus).

The male above is an older specimen with a considerable amount of pruinosity hiding any identifying marks. Moreover, the final arbiter of damselfly species are the male's claspers or female's mesostigmal plates and/or the structure of the ovipositor. It seemed like a good idea to go back and take a closer look. The photo below is another male spreadwing (yes, I'm assuming the same species as above on the basis of appearance but I think it's reasonable to do so). Closeups of this damselfly's claspers are depicted in the succeeding two images. Note how the bottom claspers are very thin; this suggests a Swamp Spreadwing (Lestes vigilax), as per the Field Guide to The Dragonflies and Damselflies of Algonquin Provincial Park and the Surrounding Area. And if I zoom in on the upper claspers, the teeth match the drawings shown in the book for this species.

It seemed like an even better idea to follow correct scientific procedure, capture a specimen, and examine the claspers in more detail in the field. I think the damselfly below is young Swamp Spreadwing male: the colors on the thorax and abdomen are visible and match those in the color drawing in the field guide. More importantly, note the claspers ... I took closeups from several different angles. The upper and lower claspers are the same as on the spreadwings in the images above and as depicted in the book. So despite the fact that the two damselflies look quite different, I can only conclude they are the same species.

The next three photos depict a female (note the ovipositor) Spotted Spreadwing (Lestes congener). This time it's safer to go by general appearances, this is the only spreadwing species with two spots on the side of the thorax.

Three views of a male Spotted Spreadwing (Lestes congener). This damselfly had a few preferred perches on the shoreline grasses and despite its relatively small size (about 35 mm) it was surprisingly aggressive with regard to defending its turf. It took on all comers, not only damselflies of other species larger than itself but even intercepting and chasing a White-faced Meadowhawk that had the temerity to approach too closely.

Dorsal and ventral views of the Spotted Spreadwing's claspers.