Sunday, June 3, 2018

Species Spotlight: Spiny Baskettail—New for Anacortes!

A couple days ago, Betsy and I went to Cranberry Lake to see how dragonfly season was progressing. The activity was high, especially among Pacific Forktails and Four-spotted Skimmers. This was discussed in a previous post:

We also saw some American Emeralds, which are always fun to see because they are fairly uncommon and have a short flight season. We saw one land in a tree, and another in the grass. The one in the tree was indeed an American Emerald. See the following post for more information on this species:

It turns out that the one in the grass was actually something completely different. Here's a look at it:

This is clearly a baskettail—and a female at that, judging from how stocky the abdomen is near the base, where it joins onto the thorax. Notice a projection extending downward near the tip of the abdomen, which is enlarged in the next shot:

This projection, or "genital plate" as it is called, is used to hold an egg mass produced by the female. Here's a female we saw in Oregon a couple years ago in the process of making a large egg mass at the tip of her abdomen:

Once she has a good-sized egg mass she flies over the water, diligently looking for a fish-free place to drop it off. The egg mass in this picture was dropped off in this way, but even with all the precautions taken by the female the eggs were gobbled up immediately by a waiting fish. We saw dragonflies at Cranberry Lake with prominent egg masses, but had never seen one close up before to determine the species.

Here's a better look at our new species:

The identification is a little tricky because we're dealing with a female, but there are basically two possibilities—a Spiny Baskettail or a Beaverpond Baskettail. If we had a male the call is easy, because the Spiny male has simple appendages, whereas the Beaverpond male has pistol-shaped appendages. The females of both species have simple appendages, however, so this nice field mark can't be used. Instead, we note the color along the back border of the head. In this individual it is black, as is pointed out in the following photo:

This border area would be yellow in a Beaverpond Baskettail female.

All in all, we were pleasantly surprised to find this new species at our familiar lake:

You never know what you're going to find when you go out into the field!

For more information on basketballs, emeralds, and many other west coast species, check out my field guide at the following link:

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