Sunday, August 14, 2011

Cherry-faced or Ruby Meadowhawk (Sympetrum internum or S. rubicundum)

Cherry-faced or Ruby Meadowhawk, two species that are
difficult to identify
Photo by Brad Sylvester, copyright 2011. Do not copy.
One of the most accurate ways to determine species is to look directly at the DNA which is after all, the stuff that makes a species different than any other. This is not a tool that was available when most species that we know today were classified, however. Instead, entomologists carefully detailed the most minute morphological variations (differences in shape or appearance) between the specimens they examined and separated them into groups or species based on these differences. Within a genus, these differences may be very small indeed. For some, in fact, it can be quite difficult even for true experts to distinguish between them.
When you think about people, there are characteristics that are specific to region of origin that can with some reliability distinguish someone of Native American heritage from someone of Chinese ancestry, yet we are one species. The point that I am trying to make here is that some of the animal species descriptions identified may have morphological differences that are smaller than typical human variations. It’s reasonable that some mistakes were made in establishing species. Even before the advent of DNA testing and sequencing, it was not entirely unusual for scientists to make changes to previously described species based on new evidence or even a very close re-examination of old evidence.
In trying to pin down a dragonfly species that I found in my yard, I happened upon a case where this may be about to happen again.
The insect pictured above is a dragonfly. You recall how we determine whether it is a dragonfly or a damselfly, of course, if you follow this blog regularly. If not, here’s the post with a refresher course. More specifically, this insect falls within the taxonomical Family called Skimmers (Libellulidae) and we can even get to the Genus called Meadowhawks (Sympetrum). From there it gets tricky.
Photo by Brad Sylvester, copyright 2011. Do not copy.
There are several Meadowhawks whose general coloration matches my photos. To get a firm ID between four possible Sympetrum matches, I’d need to look very carefully at the shape of the reproductive organs located at the tip of the tail and a feature called the hamules, located on the underside of the abdomen at its thickest part right near where it joins the thorax (circled in the photo). Even then, the ID might be less than certain, says
 The specific shapes of these features, along with the color of the face can help separate  the four similar species: Sympetrum obstrusum (White-faced Meadowhawk), Sympetrum rubicundum (Ruby Meadowhawk), Sympetrum internum (Cherry-faced Meadowhawk), and Sympetrum Janeae (Jane’s Meadowhawk) which was split out as a separate species from the Cherry-faced Meadowhawk in 1993.
Caudal appendages (male), used for mating
Photo by Brad Sylvester, copyright 2011. Do not copy.
It’s a near thing and the New Hampshire Dragonfly Survey protocol calls for a specimen to be delivered to the survey coordinator in order to confirm the specific species. In this case, I’ve got decent photos of both the tip of the tail and of the hamules, both from several angles. This was fairly difficult camera work, by the way, and involved me chasing this Meadowhawk from place to place to get the shots. Meanwhile, one thing we do know for sure is that it is a mature male. Females and immature males are decidedly more orange in color, as you can see in the photo below (labeled as immature male or female) which I also happened to find in my yard on the same day.

The immature male and the adult female of these species are
quite orange compare to the adult male.
Photo by Brad Sylvester, copyright 2011. Do not copy. says it requires a microscopic examination of these features to differentiate these Meadowhawk species precisely. Therefore, I can’t pin it down beyond saying I believe it is either the Cherry-faced Meadowhawk or the Ruby Meadowhawk. Getting back to the beginning of this post, there is some doubt about these species being separate, especially the Ruby Meadowhawk and Cherry-faced Meadowhawk according to this abstract of a study by E. Pilgrim and C. Von Dohlen published in the Annals of the Entomological Society of America which states that “genetic distances between individuals of S. internum and S. rubicundulum were small or nonexistent.” Which leads one to wonder whether these might be prime candidates for an upcoming species consolidation – which, of course, would render my indecision moot. At present, I simply don't have the equipment to distinguish between these species.

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