What's That Bug? does not endorse extermination

slug-like creature
Mon, Dec 29, 2008 at 3:02 PM
Hi,
I found this little guy under a log at my aunt’s house in central Oklahoma this summer. I see these guys pretty often, but have no idea what they are. They leave a trail of slime like a slug, but don’t have any eye-stalks, and they make little “webs” out of their slime. Any help you can provide would be much appreciated. Thanks for the great site, and happy holidays.
Josh Kouri,
Oklahoma City , Ok.

Big Mystery

Keroplatid

Hi Josh,
We are not certain how to classify your mystery organism. We don’t believe it is a mollusc, so would rule out that it is a slug. We also don’t believe it is an insect, though some larval insects are very uninsectlike, including many larval flies, commonly called maggots. This might be a fly larva. It also doesn’t seem very wormlike or leechlike to us. For now, we would say perhaps this is some type of fly larva, but we are far from certain. Perhaps our readership will come to our rescue. Meanwhile, is it possible for you to tell us how large this organism is?

The ones I’ve seen range in size from about 1/4 inch to one inch. The one
pictured was about 3/4 of an inch. Hope this helps. I’ll see if I have any
other pics.

Identification: December 31, 2008
Daniel:
Well, the description of the behavior is more helpful than the image in this case. You are quite right about it being a fly larva, most likely that of a fungus gnat in the family Mycetophilidae. Some species are known to build mucous “webs,” most notably the bioluminescent ones in Waitomo Caves in New Zealand. This one sure ‘looks’ like a slug….
Eric Eaton

Update:
January 1, 2009
Hi,
I was looking at some of my older pictures today and realized that the slug-like creature is not what makes the “webs”, and the one pictured is the only one I have seen. The creatures that make the “webs” are more worm-like, and the lengths I gave you are for the worms, as I have only seen one of the slug-creatures. I still don’t know what either of the creatures is, and I hope you guys can help. Sorry for the mistakes. Thanks for the awesome site, and happy New Year.
Josh Kouri

Fungus Gnat Larvae

Fungus Gnat Larvae

Hi Josh,
Eric Eaton wrote in to say that based on your written description, your creature was a Fungus Gnat larva in the family Mycetophilidae. That would mean that your original image is still a mystery and the new photo which shows the webs would be the Fungus Gnat larva.

fungus gnat larvae update
Fri, Jan 2, 2009 at 11:31 AM
Hi,
When I saw that you guys identified the “worms” as fungus gnat larvae I decided to look for better pictures on the internet.
The pictures I found looked a lot different from what I have been seeing. Is it possible the “worms” are some other type of fly or gnat larvae, or even something completely different? Thanks again for all you do.
Josh Kouri

Update: January 5, 2009
Daniel:
Saw the update that the image is not what is making the mucous webs. Well, I would say that the image is that of a slug, then, and it shouldn’t be that hard to ID. It is probably an introduced European species that has spread via commerce, ship’s ballast, etc.
Eric

Update:  June 2, 2017
Thanks to a comment from Rafaela, we are able to identify this as a member of the family Keroplatidae, the Predatory Fungus Gnats.  According to BugGuide:  “Larvae are predaceous or mycophagous; they spin hygroscopic webs to collect spores or small invertebrate prey. Predaceous species kill their prey with an acid fluid (mostly oxalic acid) secreted by labial glands and deposited in the droplets of their web; mycophagous larvae also have acid webs and occasionally feed on pupae of their own species or on dead insects. Larva of a Tasmanian species lives endoparasitically in land planarians.”  

What's That Bug? does not endorse extermination
Location: Oklahoma

3 Responses to Unidentified Sluglike Mystery Organism and Fungus Gnat Larvae or Keroplatid

  1. Alan H says:

    looks like a terrestrial flatworm of some kind.

  2. Rafaela Falaschi says:

    It’s a keroplatid

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