Naturespeak A naturalist's view of the world

June 6, 2010

The Dragonflies of the Dollardock

Filed under: Uncategorized — wykes @ 8:03 pm

Although the brightly colored Spatterdock flowers captured a majority of the eye-time from the end of my Dollar lake dock, the dragonflies claimed a close second. As the day grew warmer and brighter these masters of the air grew warmer and brighter as well. By late afternoon they were in full gear – hunting, perching, and making little dragonflies with equal gusto. With at least a half a dozen species darting back and forth there was nary a dull moment at dock’s end.

Dragonflies, and their smaller cousins the damselflies, are sun-worshippers. Sunny windless days offer the best type of weather for observing them and fortunately three out of my four days at the lake fit this description. I can’t claim to identify all of the species hanging around my dockside, however. Apart from the passing patrol of an occasional Green Darner, the inquisitive hand-perching of a shy female damselfly (see here), and the ceaseless activity of one unidentified and hyperactive green-eyed species, only two of them captured particular attention.

The first, called a Chalk-faced Corporal (see above), chose the end of the dock as a base for patrolling the lily pad field. This handsome male was engaged in that most typical of dragonfly behaviors called flying sorties. Using a single location as a base, this dragonfly would fly out over the “killing field” to sweep up, or investigate, passing prey and then return to the starting location. Like a jet fighter flying sorties, he patrolled a short loop and returned to base. A few moments of sun basking recharged the fighter fuel necessary to commit to another flight. He did this over and over until the place was rendered preyless, at least in his view, and he then moved on down the shore.

Keeping up with the military theme here, the Chalk-faced Corporal is so-named for the duel blue corporal stripes evident on his thorax just behind the head. The light colored pug face accounts for the “Chalk-faced” part of the name, although it sounds more like one of those uncomplimentary bunkhouse nicknames.

The most common members of the dock-end dragon clan were the equally pale-fronted Dot-tailed Whitefaces. These small dark dragonflies lacked the impressive size and rank markings of the Corporals, but out-numbered them by a factor of ten. The bright white facial markings, dark bodies, and the single light-colored dot on the 7th abdominal segment are the distinctive identifying marks for this species (see here). The females are lighter colored than the males, but the literature is clear on the point that the “older females become very male-like in appearance.” I could say that this statement applies to people as well, but I wouldn’t dare elaborate on that point.

During my few days in their company, the dominant Whiteface activity was courtship. The males (as least they looked like males!) were continually chasing off rivals. One especially feisty individual chose the tip of our fishing pole as his lofty observation post (see beginning picture). He did his best to clear the immediate vicinity of the boat for the approach of a ripe and willing female. Unfortunately, one of those rival males snagged one of those lusty females just before it entered the fishing-pole-male’s domain. There, just out of view behind the boat, he romanced that female and went merrily on his way.

The mating process differs slightly between dragonflies, but in the case of the Whitefaces it was relatively short. The male grabs the back of the females head with a pair of clasping organs located at the end of his body (see below). The female, suspended by the males grasp, turns her abdomen up and reaches into the male’s sperm pouch to transfer the fertilizing agent to her own body. This formation, known as the wheel formation, is unique to dragon and damselflies. The pair can, and often does, fly while so joined. In some dragonflies the male keeps his grip even as the female lays her eggs.

Whitefaces apparently don’t linger in this pose. The male broke off the engagement within a few minutes and the female immediately started laying eggs on her own. One by one she dipped the tip of her abdomen into the surface and placed her charges into the weedy waters – insuring another generation of dockside dodgers to carry on the tradition.

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