Face-off

You rarely see two male dragonflies get this close without doing battle.

The male 12-spotted skimmer on the right attempted to usurp this perch from the male on the left, but was chased away.

The male 12-spotted Skimmer on the right attempted to usurp this perch from the male on the left, but was chased away.

There is a reason the male on the left wants that particular position — it’s somewhat shaded, and it’s a hot day with the sun directly overhead and high humidity.

Notice how the dragonfly has flexed his abdomen downward and perches behind the stake to shade himself somewhat.

Notice how the dragonfly has flexed his abdomen downward and is perched behind the stake to shade himself somewhat.

When he is perched this way, it gives me a much better look at his whole face. Now all we need is some names for those parts.

12-spotted skimmer face

Here’s a diagram I made in Photoshop that I hope accurately labels the parts.

12-spotted skimmer head-labeled

Starting at the top, you can see the short antennae emerging just above the darkened area of the vertex (triangle between the eyes), in which the primary light sensing ocelli are placed. Ocelli (there are three of them) are simple eyes (i.e., not compound) are used to detect changes in light intensity and duration, not for visual acuity.

The front of the dragonfly’s “face” is composed of the dark, bumpy frons and the much paler, two-segmented clypeus, which lie above the upper lip or labrum (looks like a mustache on this dragonfly).  This part of the face is the only part we usually see in horizontally perching dragonflies.

The real chewing apparatus of a dragonfly is composed of the mandibles and the maxillae (probably named for their similar roles in mammals) which lie directly below the labrum.  They are attached at the side of the head, coming together in the middle for tearing/crushing action, and when fully opened provide a wide gape entrance to the mouth.   No wonder they can chew up their prey so quickly and effectively.

Thanks to a hot, hot day and a 1917 textbook on dragonfly anatomy, I now know a little more about dragonfly faces.

7 thoughts on “Face-off

  1. I’ve never really thought about insects getting hot but I don’t know why they wouldn’t. I scared several off yesterday and they flew up into some birch trees. It was brutally hot at the time, but I don’t know if they were roosting in the shade of the trees or not.

    • Bees hide most of their faces from view too (like dragonflies). I only ever see the tops of their heads, as they bury their proboscis in a flower. You would have to get on the ground and shoot up toward the flower to get a look at their whole face. So many future projects…

  2. I love that shot of the two males. It’s always fascinating to see interactions and this image has the added benefit of a beautiful background. Thanks for identifying all of the parts of a dragonfly’s face. Given the amount of time that I have been spending with dragonflies, it’s nice to know what to call the different parts (though I rarely get such a clear, close-up view of the face as you did).

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