Currently viewing the category: "Black Scavenger Flies"
What's That Bug? does not endorse extermination

Subject: Flies that love “docking”
Location: Santa Barbara, CA
April 6, 2016 4:54 pm
In the past two weeks or so (since mid-February), my apartment in Santa Barbara, CA has become home to these little flies (~3mm long) that seem to like to spend all their time docked posterior-posterior. Solo, they’re pretty active and prefer windows, mirrors, or just flying around roughly at head height; docked, they like walls and (especially) ceilings, and seem to spend 8–10 hours totally stationary—though when they do move, they do so as one, rather than separating first. They must go somewhere to hide overnight, because I only see them during the day. Also, unlike the fruit flies that sometimes invade my apartment, I’ve never figured out what these eat.
I’ve just never seen anything quite like this—in fact, for the first week or so, I thought it was a single long, skinny insect, and was very surprised the first time I saw that it was actually a pair. Maybe you can shed some light on what these are?
Signature: Curious in California

Probably Mating March Flies

Mating Minute Black Scavenger Flies

Dear Curious in California,
We believe these Dipterans are mating March Flies, but we really wish your image had higher resolution allowing us to see the details better.  March Flies in the family Bibionidae are sexually dimorphic, meaning there is a distinct visual difference between the sexes.  Males have much bigger heads and eyes than females, and the head in the upper Fly in your image is difficult to discern.  According to BugGuide, the species is found in Santa Barbara and BugGuide has an excellent image of a mating pair.  Of the family BugGuide notes:  “Adults emerge synchronously in huge numbers and often form dense mating aggregations. Males form loose ‘swarms’ and copulate immediately with females as they emerge from the soil. After mating, female bibionines dig a small chamber in the soil with their fossorial fore tibiae, lay eggs, and die within the chamber (
Plecia lay eggs on the soil surface). Adults are short-lived (3-7 days).”  Perhaps the most notoriously famous March Flies are the Love Bugs in the genus Plecia from the southeast, including Florida, that emerge by the millions and seem to be perpetually in flagrante delecto.  While we were much amused at your “docking” euphemism, since the insects in your image represent opposite sexes, the term is really not accurate.  A much better visual representation can be found in these mating Big Poplar Sphinxes.

Possibly March Fly

Minute Black Scavenger Fly

Thank you for the reply! I had in fact wondered whether they were love bugs (since I was able to guess what they were really up to), but the pictures I found online looked different enough to what I was seeing—and the stated range on Bibionidae also being larger than the 2–3mm of my “guests”—that I wasn’t sure. Unfortunately, the only camera I have access to is the one on my outdated iPhone, so those pictures are probably as high-resolution as I can get. In person, even under low magnification, I can’t quite tell whether their heads (which are both under 0.5mm) are different sizes. However, on the basis of descriptions like “The male and female attach themselves at the rear of the abdomen and remain that way at all times, even in flight” (from Wikipedia), which comports exactly with what I’m seeing, I’m satisfied that these are in fact Bibionidae. So, thank you again for resolving the mystery.

Update:  April 9, 2016
Thanks to a comment from Cesar Crash, we agree that these are mating Minute Black Scavanger Flies in the family Scatopsidae, which is represented on BugGuide where it states:  “Larvae feed on decaying organic matter, such as detritus or excrement.”  Minute Black Scavenger Flies and March Flies are classified together in the infraorder Bibionomorpha.

What's That Bug? does not endorse extermination

Curious Girl does Spring in Europe (New species for WTB — I think)
Location:  Porto, Portugal
March 20, 2014
Hope you will forgive me Daniel for sending you the pictures this way. You can open just one mail and then pick & choose, and it’s much easier for me as I would not probably get to it if going through the web form. I do not know what most of them are and would like confirmation on those I think I might know. :~)
Seems the slow season is over!
Anyway…
I have some decent pictures of some insects both in Germany (Hanau this time) and Portugal (Porto though some from Tras os Montes soon) before I left (currently in Istanbul) so I will share a few with you, including a few I thought were just flying ants but turned out to be something far more interesting and even quite nice pictures so I am glad I bothered. Plus I do not think they are represented on the WTB site.
They are Ensign or Black Scavenger Flies of the family Sepsidae. 🙂 And like the big Crane Flies seem to have vestigal wings. Apparently all females too.
They are Ensign or Black Scavenger Flies of the family Sepsidae. 🙂
And thus concludes part one of CG’s Spring 2014 Euro tour. :~)
Thanks & Happy Nowruz Daniel! 🙂

Black Scavenger Fly

Black Scavenger Fly

Dear Curious Girl,
Thank you for your multiple attempts to get this plethora of new imagery to us.  You are correct that we do not have Black Scavenger Flies in the family Sepsidae represented on our site, so we are posting several of those images and creating a new category.  According to BugGuide:  “Small, shining blackish flies, sometimes with a reddish tinge; spherical head; abdomen narrowed at the base. Many species have a dark spot along the costal margin of the wing near the tip.” BugGuide also notes:  “Larvae live in excrement and various types of decaying matter. Adults found near material that the larvae feed on.”  It is somewhat difficult for us to create multiple postings from a single email, so for the time being, the only posting we are creating with these images is the Black Scavenger Fly posting.  When time permits, you can try resubmitting other images using our standard submission form, limiting each submission to a single species, and ensuring that location information is correct for that species.

Black Scavenger Fly

Black Scavenger Fly

What's That Bug? does not endorse extermination