Wednesday, April 29, 2015

Rambur's Forktail

One of the first odonates we see each year is the Rambur's Forktail.  In terms of coloration, it is similar to the Western Forktail that is common in Washington – green thorax with a blue tip to the abdomen – but the ranges are quite different.  Notice that the abdomen is black above and yellow below, with a nice straight line demarcating the two colors.  Here's a look at a male Rambur's Forktail:

A male Rambur's Forktail at the Gilbert Water Ranch.  Notice the hamules under segment 2 of the abdomen.

The eyes are similar to those of the Pacific Forktail – black above and greenish-blue below.

Female Rambur's Forktail can look a lot like a male, in which case they are said to be andromorphic (male form).  An example is shown below:

An andromorphic female Rambur's Forktail at the Gilbert Water Ranch.

Notice the flat bottom to segment 2 (S2) of the abdomen.  Thus, this individual lacks hamules, which indicates clearly that it is a female.  In the photo of the male above, the hamules are seen prominently on the bottom of S2.

Females can also look different from the males, and in this case are referred to as heteromorphic (different form).  Here's an example:

Heteromorphic female Rambur's Forktail.

Notice the orange thorax with the black front stripe, and the lack of hamules under S2.  As this individual matures it will become more greenish-brown.

Monday, April 13, 2015

Happy-face On My Finger

I have many pictures of the Happy-face Dragonfly sitting on my finger.  I decided to convert one of them to a drawing.  Notice the paddle-shaped appendages – which are responsible for its official common name, the Paddle-tailed Darner – and the presence of a light-colored spot on the tenth segment of the tail (abdomen).

The official name, Paddle-tailed Darner, isn't particularly apt because a number of different species have paddle-shaped appendages.  For example, the Shadow Darner, Walker's Darner, and the Lance-tipped Darner all have appendages with a similar paddle shape.  This leads to confusion because people often think that paddle-shaped appendages must be distinctive to the Paddle-tailed Darner, and are surprised to find the same shape in other darners.

In addition, the use of "tailed" in the name is unfortunate, because "tail" usually refers to the abdomen, not the appendages.  As an example, the Common Whitetail has a white abdomen (tail); similarly, the Red-tailed Pennant has a red abdomen (tail).  On the other hand, the Brush-tipped Emerald has appendages (tips) that are brush shaped.  So, the Paddle-tailed Darner has a name that is not particularly appropriate – of course, I think it's official name should be the Happy-face Darner!

It's been a long time since I seen one of these guys, much less had one on my finger.  I'm looking forward to becoming reacquainted with them later this year.  In the meantime, here's a YouTube video slideshow of a variety of dragonflies on my fingers:  Slideshow.