Friday, April 8, 2011

My first flying odonate of the year! (and a bunch of other things)

In my previous post about the Pacific Northwest’s first fliers, I lamented about the cool, wet spring that we’ve been having, and about not seeing any odonates yet. The forecast for today was sunny skies and highs approaching 60° F—still chilly for this time of year, but promising, so I checked out a wetland mitigation/storm water retention site in Vancouver. It isn’t what I consider a great place for odonates, but it’s convenient for a local excursion.

There were no flying odonates evident as I walked through the weedy/brushy margins of the site where I imagined recently emerged dragonflies and damselflies would be hanging out to feed and soak up the rays. There were a lot of other flying insects though. The Diptera (two-winged flies) in particular were out in force and had me wishing that I knew more about them. The most interesting among them was some sort of small robber fly (Asilidae) that I had never noticed before. These things have a really long proboscis relative to the body size which gives them a rather comical look. There were a lot of them and most that I looked at closely were feeding on some other insect. There was also amorous behavior going on. Here’s a series of shots of the robber fly. Leave a comment if you happen to know what it is. [I was informed by a couple of readers that these are not actually robber flies—be sure to see the postscript down at the bottom.]

I presume this is a male of the mystery robber fly.
This one shows the proboscis better.
I think this is a female. This one is enjoying the blooming Oregon-Grape.
A male robber fly with prey.
Now this I think is simply comical. Here’s a pair of the mystery robber fly copulating while the female is
grasping (and I assume feeding on) a prey bug. I’m also impressed with the male hanging from his front
legs. I won’t comment any further...

Here are some other dipterates that were enjoying the sun...

A bombyliid on the left and a syrphid.

And some sort of wasp...

And a couple of non-avian vertebrates...

A Common Garter Snake (Thamnophis sirtalis) on the left and a Pacific Chorus Frog (Pseudacris regilla).

And finally, as the title of this blog suggests, I did turn up one flying odonate: a teneral (recently emerged) male Pacific Forktail (Ischnura cervula) which flew up from some emergent sedges as I was wading into the water...

A teneral (recently emerged) male Pacific Forktail (Ischnura cervula) in Vancouver, Washington, on
8 April 2011.

Over the next few days, those dull grayish areas on the thorax and abdomen will turn blue (like those small spots above the eyes) and the eyes will turn black and green. Compare this individual with a mature male in a recent post.

So that was a couple hours today in a nearby wetland. It always feels good when I find my first adult odonate of the season. Somehow it just feels like everything’s going to be okay.

Postscript, 8 April 2011

Mike Patterson at North Coast Diaries pointed out that the robber flies photographed here are probably dance flies. Browsing through, I had to agree, and there are several photos of Empis in Empididae that look like a good match. Males actually present a nuptial gift of prey before copulating and that must be what the female of the copulating pair is holding. Before I had a chance to add this postscript, Steve Collins confirmed that these are dance flies and also suggests the genus Empis. Thanks to both Mike and Steve!


  1. Great shots! I especially like the depth of field on the garter snake pic. Beautiful!

  2. Your 'robber' is a dance fly. I believe it's an Empis sp. The male gifting a prey item to the female is classic. Some Empis wrap the prey in silk, and sometimes they give the female an empty silk balloon. Apparently even when that happens, the female doesn't reject copulation. Great photos.

  3. Fantastic photos! I saw a robbery fly very similar to this today.

  4. @Steve Collins Another reader just pointed out by e-mail that the robber flies are actually dance flies. Browsing through, I thought Empis was a good match too. Thanks for the input! I'm about to add a postscript...

  5. The 'wasp' looks like a cuckoo bee, genus Nomada.

  6. Rob Cannings was kind enough to send me note and let me know that the dance fly prey item is a male march fly (Diptera: Bibionidae: Bibio sp.) and that the bombyliid is Bombylius major. Thanks, Rob, and again thanks to all who helped out with the IDs!