Posting on behalf of a neighbor who asked:

Can anyone identify this insect? It's about 3/8" long. There are, it seems, hundreds flitting low over our lawn. There were none 2 days ago.

This is the Northern California Bay Area Peninsula.


  • $\begingroup$ $\frac{3}{8}$'' is a weridly accurate measure so just to confirm, it was $\frac{3}{8}$ of an inch, that is 0.95 cm, is that right? $\endgroup$
    – Remi.b
    Commented Oct 1, 2016 at 1:16
  • $\begingroup$ Yes, " indicates inches. So about 1 cm. $\endgroup$
    – rrauenza
    Commented Oct 1, 2016 at 3:15
  • $\begingroup$ One concern is that they are swarming termites. $\endgroup$
    – rrauenza
    Commented Oct 1, 2016 at 14:51

2 Answers 2


Great pictures. First, fly or wasp?

In the second picture, under the head you don't see jaws of a wasp, but do see a bit of a tongue-like organ, like a fly. Further down, you can see that there are only 2 wings. Just below where the left wing meets the thorax, you can see what looks like a tiny wing or paddle. That's a haltere, a reduced wing that vibrates to provide stability, like a gyroscope. Flys have halteres. Finally, in the first picture at the very end of the abdomen are 2 points. That ain't a stinger, it's an ovipositor. It's a fly, female, and from the size of the abdomen, gravid.

The closest I've gotten to identifying this one is Axymyia furcata http://bugguide.net/node/view/1216479. Everything matches, as well as we can see from a photo, except the coloration. Also, A furcata is associated with streams and is found in the north-east and north-central US, while, your bug was found on a lawn in CA. For more information about A. furcata than you need, there is a master's thesis available: http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=1882&context=etd.

I've looked at hundreds of fly pics to find the one I linked to above. That's the only fly I found that matches the shape of yours. Maybe it's a different fly within that genus, maybe it's just a color variation.

Their maggots live in rotten wood and decaying plant material, and the adults are mostly interested in more maggots, so this isn't a pest, just a neighbor.

Edit: furicata --> furcata, oops.

  • $\begingroup$ Can you fix furicata to furcata? (I can't -- the edit isn't large enough.) $\endgroup$
    – rrauenza
    Commented Oct 2, 2016 at 4:14

My neighbor submitted the photo to http://bugguide.net and it was identified as a sugar cane soldier fly, "Inopus rubriceps"- Female


They are from Australia and were accidentally introduced to San Francisco 50 years ago. It feeds on grasses.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .