Wood Gnat

2012 August 15

I happened to have my camera with me when I went to work[1] on July 26, 2011, and spotted this little fly on the wall in the little room between the outer and inner entrance doors[2]. It was just a touch bigger than the average mosquito, at maybe 7-8 mm long.

It was clearly a true fly (Diptera). I spent quite a bit of time browsing through all the little mosquito-like flies on BugGuide and wasn’t really finding it on my own, so I posted it for ID. And, after a few days v belov identified it as a Wood Gnat, genus Sylvicola.

People mostly ignore wood gnats, because they don’t do much to us. The larvae eat decaying wood and leaves, and the adults eat sap and sometimes are drawn to lights. And get eaten by spiders that build their webs around the lights. I’m pretty sure that this one was on the wall where I found it mainly because of the light outside over the door.

[1] We have been working on a couple of projects where we needed to record the sizes and shapes of mineral grains and air bubbles. The mineral grains were small enough to be hard to see by eye and large enough that they were awkward to look at with a standard microscope, while the air bubbles were just impractical to get onto a microscope stage in the first place. So I brought in my camera and macro lens, which was perfect for these situations. And, of course, when I saw an insect while I had my insect camera in hand, obviously I had to photograph it, right?

[2] The majority of buildings around here have a double-door system for entrances, kind of like an airlock. You open one door, go into the little anteroom usually about 5-6 feet square, then close the first door and open the second. It really helps avoid getting a blast of cold air blowing straight into the building when you go in or out during the winter. It does make it pretty awkward if you are carrying something bulky and want to get through the doors, though.

3 Responses
  1. August 16, 2012

    Where’s the ref? This post should be given a yellow card at least! The wood gnat did not come from your property and therefore it has no place here.



  2. August 16, 2012

    Augh, you caught me. I defend including it by pointing out that my house is within easy flying distance of where I work, so it *could* have gotten to my house if it tried. Yeah, I know. That’s kind of weak.

  3. Cora L permalink
    June 9, 2016

    Thank you for this! I’ve been trying to identify what this critter is for a week now – you’ve set me on the right track for working out why they’re in my house!

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