Monday, August 31, 2009

Reptiles of the Riverbank

Tame and harmless, the Garter Snake (Thamnophis sirtalis) is a common denizen of our fields and gardens. This one measured a little over a foot long, a fully grown snake can exceed two feet.

A smaller snake, only a few inches long.

Another youngster, a Snapping Turtle (Chelydra serpentina). When fully grown this turtle can measure over two feet in length and weigh in at 70 lbs ... and needless to say it won't be as docile and easy to handle.

Friday, August 28, 2009

Red Clover (Trifolium pratense)

... with four leaves. Uncommon, occurring about one in ten thousand times, but it happens. More than four leaflets are possible, I have found several specimens with five and one with six. The highest documented count is twenty-one (Shigeo Obara, Japan).

A couple of days after I took the photos of the four-leaf clover I stumbled across a five-leaf. Not in very good shape, it looks like the grasshoppers found it before I did.

Thursday, August 27, 2009

Halloween Pennant (Celithemis eponina)

The Halloween Pennant is one of our most colorful dragonflies. The reddish tint on the wings, and red pterostigmata and abdominal stripe indicate this is a male. This dragonfly has a weak, fluttery flight reminiscent of a butterfly.

A front view

Time to clean up. There was a spiderweb on the perch, and some of the strands were sticking to the dragonfly's eyes and legs.

Wednesday, August 26, 2009

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?

Wednesday, August 19, 2009

Eastern Gray Treefrog (Hyla versicolor)

Or is this Cope's Gray Treefrog, Hyla chrysoscelis? It seems the only means of distinguishing these two frogs in the field is their calls, and this one wouldn't sing for me. (An examination of the blood cells will work but I didn't have a microscope or a means of sampling its blood). This is still a youngster; I took a couple of photos of the frog sitting on my finger and hand give an idea of its size.

Here is the tree frog in its natural element. As its name suggests, the color of this frog is more commonly a patterened gray. The skin has cells called chromatophores, which contain granules of different colored pigments. Were this frog were to rest on bark the visual cues it perceives will trigger a series of complex changes, the end result being an alteration in the concentrations of the skin pigments, changing its color from green to gray.

Monday, August 17, 2009

Band-winged Meadowhawk (Sympetrum semicinctum)

The amber wash at the base of the wings makes Band-winged Meadowhawks easy to identify in the field. Based on my amateur observations, these meadowhawks seem to be less common locally than other Sympetrum species. This female was photographed in a garden a few hundred feet from water.

Females perching on vegetation on the shore of the Moira River, at the southeast corner of the dam. Upon further exploration I found that this is a favoured breeding site. Despite the Band-winged Meadowhawk's seeming scarcity at other locales this species is certainly plentiful in this small area, and over the course of a few weeks I observed several dozen mating and ovipositing pairs.

Views of a male

A female, still held in the grip of the male, ovipositing in the still, stagnant pools of water along the river shoreline. The bottom consists of large rocks, the spaces between them filled with mud and debris consisting of decaying leaves and sticks. I also observed the female ovipositing on her own, but still under the watchful eye of her mate. There were at least two other males present, and the male in these photos was constantly being contested for breeding and territorial rights.

A few more photos of male Band-winged Meadowhawks, taken at a later date than the pictures above. The population seems biased in favour of males, which outnumber the females by about three to one.

Perching on a Cardinal Flower, camouflaged against the red background ...

... and caught in action at the moment of taking flight.

Front and lateral views of a male

A mating pair in the wheel position

Closeup of the female gripped by the male's claspers

Friday, August 7, 2009

Hunters of the Lakeshore Skies

There was no choice but to take the following two pictures while this dragonfly was on the wing, because, much like the large darners, these guys fly and fly and fly ... This one seemed to prefer patrolling back and forth along the margin of the lake, staying a couple of feet above the water where there were no emergent plants. I expect to get a better photo in the near future as these dragonflies are very curious, stopping to hover in one place for a few seconds while looking me over (maybe wondering if I'm edible?)

The colors and shape of the wings are clear enough to identify this as a Wandering Glider (Pantala flavescens), having the reputation of being the most widely distributed dragonfly in the world. As their name suggests Wandering gliders are migratory and I don't see them every year.

Rather than staying on the wing for long periods like darners, dragonflies such as the skimmers below usually prefer to sit on a favourite perch, darting out to snatch smaller insects that happen to fly past.

Slaty Skimmer (Libellula incesta), male

Twelve-spotted Skimmer (Libellula pulchella), male

Left: Widow Skimmer (Libellula luctuosa), male
Right: Eastern Pondhawk (Erythemis simplicicollis), female

Widow Skimmers are gregarious and tame. They don't startle easily, making them good subjects for beginners to photograph. This female Widow Skimmer didn't mind posing for a mug shot.

An Eastern Pondhawk (Erythemis simplicicollis) eating dinner. I've found that dragonflies seem to pay less attention to their surroundings when they are busy chowing down, and this is a good time to sneak up on them for a close shot. This is a young male, some green is still visible on his thorax. As he ages the pale blue pruinosity typical of the adult males will cover his entire body.

An even younger male, he's only developed a bloom on his abdomen.

Damselflies and dragonflies belong to the order Odonata, which means "toothed jaws". This female Tule Bluet (Enallagma carunculatum) is eating what appears to be a small whirligig beetle. The beetle's hard exterior wings aren't much defense against the damselfly's natural cutlery.

A female Powdered Dancer (Argia moesta) consuming its prey.

When dragonflies aren't hunting and eating they're busy starting the next generation. The following two photos are mating pairs of Halloween Pennants (Celithemis eponina) in the wheel position. Much like their table manners, there's no civility or consideration when it comes to dragonfly love ... the female's eyes and head may end up getting gouged and punctured by the male's claspers. While this may seem terrible from our human perspective, evolution is all about whatever works to perpetuate the species and according to the fossil record dragonflies have been around for a few hundred million years.

Mating White-faced Meadowhawks (Sympetrum obtrusum)

As often as not, the hunter becomes the hunted; this is a Robber Fly having a bluet for lunch. Robber flies are in turn pursued by the damselflies larger odonate cousins. Robber flies and dragonflies lead similar lives and exploit related niches in the ecosystem. Although a true fly possessing only one pair of wings, note how the robber fly's appearance ... the large compound eyes, hairy basket-like legs, and long wings and abdomen ... tends resemble that of a dragonfly. Now that's evolution in action.