Sunday, October 11, 2015

Four-spot Capture

One of the slow-motion videos I took this summer showed a Four-spotted Skimmer chasing and catching a small fly.  The way he did it was a bit surprising, though.  He waited until the fly passed him, turned and flew ahead of the fly, and then approached it head-on for the capture.  Here are some frames from the video that document the event.

In this frame, we see the small fly (red dot) ahead and to the right of the skimmer.  A blue dotted line goes from the head of the dragonfly to the prey.  The fly is traveling in a straight line at uniform speed – apparently oblivious to the potential danger in its vicinity.

In this frame the dragonfly is basically in its same position, soaring motionless in a headwind, as the fly gets closer.

Here the fly is passing the dragonfly, while the dragonfly continues to hold its position.

As the fly continues on its path, past the position of the soaring predator, the dragonfly suddenly initiates a turn to go toward the potential prey.

Now you might think the dragonfly would overtake its prey from behind and make the capture that way, but instead it zips ahead of the prey and turns to face it, as we see in this frame.

The dragonfly now drops below the prey, and puts itself in a position to rise and capture the prey head-on, which it does just a split second after this frame.

Of course, in real time this happened so quickly that no details could be made out.  I knew a capture had occurred, but that was about all.  Fortunately, the slow-motion video allowed for a detailed look at just how the dragonfly effected its capture.  Cool!

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