Friday, February 4, 2011

Zenithoptera: The Morpho of the Dragonflies

I’ve always intended to keep a primarily Pacific Northwest (of North America) focus to this blog, or at least stick to topics relevant to odonates in this region, but this is one of those times that I’ll deviate from that scope. There are just so many cool odonates in other parts of the world worth sharing, and the subject of this post is in the northwestern part of South America, so I call it good.

One of my most memorable encounters with dragonflies was the first and only time I saw a member of the genus Zenithoptera. I was in the Amazonian lowlands of Ecuador with a couple of friends walking into a sunny clearing with a low, boggy area. Around a small pool of water were these little dragonflies with stunning velvety blue upper wing surfaces. One of my companions had found this spot on a previous trip and wanted to share. The other trip mate told us later that he thought those little blue gems were butterflies and, while admitting that they were very beautiful, wondered why we were so intent on photographing them. He was shocked when he got a good look and realized that they were, in fact, odonates.

There are four recognized species of Zenithoptera which range over much of northern South America—one getting as far north as Costa Rica. The one species that I’ve seen (and the one pictured throughout this post) is Z. lanei and, besides Ecuador, is recorded from Peru, Brazil, Venezuela, Paraguay, and Argentina.

Zenithoptera lanei. Top to bottom: male side view;
male front view (looks like a flower to me); male
with wings raised; pair copulating.
If you focused only on the body of Zenithoptera—the head, thorax, and abdomen, you’d think these were among the dullest, least interesting odonates that you’ve ever seen. Ah, but the wings are what make them so stunning with that kind-of-hard-to-describe silvery, slightly iridescent blue over the upper surface with just a hint of pale patterning. The color on the females’ wings is a vivid, almost metallic, deep blue with more obvious pale patterning. The underside of the wings is very dark—almost black, and that vague pale pattern on the upper surface shows very clearly on the underside. The wings are reminiscent of the blue species of Morpho butterflies, although Zenithoptera lanei are much smaller—only about an inch long with a wingspan of about two inches.

But, wait, there’s more! The wing coloration isn’t even the coolest feature of Zenithoptera. I mentioned in another recent post that you’ll find exceptions to almost every “rule” as you delve into the world of odonates, and this is one of those cases. One of the basic differences between dragonflies and damselflies is that dragonflies perch with the wings open and out to the sides while damselflies typically perch with their wings closed over the abdomen. There are actually a lot of exceptions to that rule among the damselflies, especially in the tropics, but, at least in the New World, only the Zenithoptera among the dragonflies ever perch with the wings closed—straight up over the thorax. This is what puts the “Zenith in Zenithoptera. It’s really a very odd thing to behold the first time you see it.

Zenithoptera don’t always perch with the wings closed. During my brief experience with them in Ecuador they spent most of their perching time with the wings fully open (and actually drooping quite a bit like some dragonflies do, looking like flowers when viewed head-on) exposing that beautiful blue color, and only closed them occasionally for short periods. I don’t think anyone really knows why they do it. If the wings were kept closed most of the time I’d suspect it was to avoid being spotted by predators (particularly birds), but the ones I observed kept their wings open a majority of the time. To me it almost seemed to be a signal among the Zenithoptera, but what exactly was being signaled, if that’s what it was, is beyond me. Even pairs that were copulating alternated between open and closed wings. When the male closed his wings, the female’s head would be hidden. I wonder what she thought about that.

There is more Zenithoptera weirdness—are you sitting down? This next trick really blew my mind. I was photographing a female perching alongside the pool when she raised only the hind wings to the folded vertical position, but left the fore wings in the open position. After a couple of seconds the hind wings were dropped for a while just like the fore wings, then she did it again. She repeated this several times while we watched her, periodically raising only the hind wings for two or three seconds each time, and luckily I kept my head well enough to photograph each state.

Female Zenithoptera lanei. All wings in the open position on the left; only the hind wings raised in
the closed position on the right. What do you think she is doing?
The wing-raising behavior of Zenithoptera is well-known, but I had never heard of one raising only the hind wings. The periodic, seemingly methodical movements really seemed to be some sort of signal, but there’s no way to be sure of that. I think we had just seen this particular female copulating a minute or two earlier, so perhaps she is telling other males in the vicinity that she won’t be interested for a while. This is only speculation on my part, however. I would love to hear comments on this behavior (both the raising of all wings and the raising of only the hnd wings) if you have any ideas about it.

If I was to pick one odonate as my favorite (as I did in a recent comment on The Dragonfly Woman’s blog), I would have to go with the beautiful, stunning, unusual Zenithoptera. I hope it isn’t too long before I see them again!

Postscript

As Dennis Paulson points out in his comment, “zenith” in this case likely refers to the sky blue color of the wings, not the aiming of the wings toward the zenith of the sky. This makes sense considering that the describer, Selys, would not have seen these dragonflies in life. Thanks go to Dennis for setting me straight, but I think the behavior is very fitting of the name.

5 comments:

  1. Wow, those are gorgeous photos, Jim. That genus comes close to being my favorite odonate. In fact, a few years ago I wrote about it in Agrion, the newsletter of the Worldwide Dragonfly Association. My first encounter with it was at La Selva, in Costa Rica, where I discovered Zenithoptera fasciata in 1966 for the first records of the genus from Central America. That was one of the biggest thrills of my odonatological life. I saw several and collected a male, and when I was hiking back from the swamp, the collecting jar fell out of my pocket, and I only realized it when I got back to the field station. I was devastated, but to make a painful story much less so, I went back the next day and got another one.

    I think the "zenith" in the name actually refers to the sky-blue color of the wings, as the describer (Selys in 1877) would never have seen them in life. I never have seen one close only the hindwings as you did; that's very impressive.

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  2. @Dennis Paulson Thanks for the clarification on the meaning of "zenith" in this case. That makes a lot of sense, and I'll add a postscript about that. It's very fitting that they point their wings straight up to the sky...

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  3. Awesome! Thank you for my morning blue fix.

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  4. How timely to come across this, as I've been trying to match a (very poor) photo of a dragonfly I saw at Explornapo Lodge in Peru - clearly a Zenithoptera from the photos you have here. I'm unable to find any information on differentiating fasciata vs. lanei, however, & note from the World Odonata List that both are found in Peru. Any tips?

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  5. @Todd Z. lanei is the only member of the genus that I have experience with, but, if I'm reading my references correctly, Z. fasciata lacks the noticeable pale spots near the tips of the wings (most obvious on the underside). You're welcome to e-mail your photo to me if you'd like, but I can't make any guarantees.

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