Small, black, elongated flies mating

2014 November 19

These two flies were on the south wall of our house on October 10, 2013 (one of the last pleasant, sunny days of the year). Their combined length was only about a centimeter.

From directly above, the wings had a faintly iridescent sheen.

From their general body shape, I figured that they were related to the “March Flies” and similar midges in the infraorder Bibionomorpha, but this is a huge group of insects. In particular, I needed to find something where both the male and the female had the same sized heads, and where they had both distinct necks and fairly stout antennae. These are all somewhat unusual traits in flies (it is more typical for male flies to have huge eyes compared to the females, the necks are often hard to see, and most flies have negligible antennae).

So, I posted them on BugGuide, and John F. Carr identified them as probably “Minute Black Scavenger Flies” in the family Scatopsidae. This is apparently a family of 72 known species, with adults ranging from 0.5 to 5 mm in length, and the larvae all live in decaying material (including animal droppings). The adults are often found in flowers. Or, as these are doing, mating on warm, flat surfaces. Being tiny, they are hard to photograph with sufficient detail to tell what species they are, so it looks like this is as far as we are going to go.

4 Responses
  1. November 19, 2014

    I’ve been following you for quite some time, but I gotta ask-why are so many of your postings of photos taken from a year ago? Did 2014 not yield any new discoveries? 🙂

    I have a hard enough time writing about something I saw last week, let alone a year ago. On the other hand, the seasonality of bugs does make writing about something a year ago more appropriate than say a month ago.

  2. November 20, 2014

    Minute Black Scavenger Flies from a family of 72 known species. Other species include:
    More Minute Black Scavenger Flies
    Really Minute Black Scavenger Flies
    Fantastically Minute Black Scavenger Flies
    Not Quite So Minute Black Scavenger Flies


    OK, This Time I’m Not Kidding, These Are The Most Minute Black Scavenger Flies I’ve Ever Seen And I’ve Seen A Lot Of Minute Black Scavenger Flies

  3. November 21, 2014

    Tim: I’m generally posting pictures from the previous year because I have a huge backlog. We really only have a significant variety of insects to photograph from about May to October, so I photograph as many as possible to make sure there are enough to post during the “insect dearth” from November to April (pretty soon now, there’s going to be a big jump from the Fall 2013 specimens to Spring 2014). Although, sometimes when I get a particularly good one I can’t wait, and end up posting it right away. As for keeping track, I have a little “‘Rite in the Rain” notebook that I keep with the camera for jotting down dates, locations, and other relevant information, which helps immensely. And the water-resistant paper is way more survivable than a conventional notebook. Aside from the water resistance, the pages are significantly stronger than regular paper and unlikely to tear out of the notebook by accident.

    KT: Ha. This is kind of reminiscent of Ted MacRae’s key for identifying North American ants. He reduced everything to Big, Medium, and Small Black Ants; Big, Medium, and Small Yellow Ants; and Fire Ants.

  4. Briony permalink
    September 29, 2015

    Thank you! I now know exactly what is going on on my ceiling.

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