Mystery Worms – Nematomorpha?

Horse Hair Worm?

Several days ago I was quite surprised to come across an unusual worm sitting on the edge of my rain barrel. Given its jerky flailing movements, on first glance I assumed it was some sort of long “inch worm” (i.e. a type of caterpillar), but I quickly realized it was something else altogether. Given my background in identifying aquatic invertebrates (what I used to do as a “job”), I’m generally not thrown off by any small creepy crawly critters I come across on my property. This worm definitely had me stumped though.

My first guess was that it was some sort of giant nematode. As such, I did some digging online to see if I could track down any types of nematode that are not only large, but also terrestrial (or at least semi-terrestrial). Most of the nematodes I’ve come across in aquatic samples (and in my worm bins for that matter) were very tiny – either microscopic, or barely visible. As I learned, there IS a family of large-bodied parasitic nematodes, Mermithidae, that seemed to fit the bill. According to the Wikipedia entry for these worms, they are most commonly parasites of arthropods (insects, spiders, crustaceans etc), but there was also mention of the fact that a few species are known to parasitize earthworms!

Ok – so I’m not really worried. In fact, I don’t even think these are mermithid nematodes at all! Another type of large nematode-like worm is the “Horsehair Worm” or “Gordian Worm”, and I’m not sure why these didn’t come to mind right off the bat – I certainly found plenty of them in various aquatic samples I used to sort through.

Gordian Worms, like mermithids, are typically parasites of various types of arthropods (grasshoppers are one of the more common hosts, I believe) – not the adult worms themselves, but the larvae that hatch out from the eggs they lay.

Since finding my first specimen, I’ve started seeing more of them – generally after rainfall (something we’ve been getting a lot of lately). I collected a couple of them today so I could take some pictures.

Horse Hair Worm?

I will be very interested to see if I can determine what poor group of critters is going to be their host this year. I tend to have a decent population of grasshoppers and crickets each year so I’ll be keeping a close eye on them once they arrive.

Of course, just to be absolutely sure these worms aren’t up to no good, I will also be keeping a very close eye on my outdoor Red Worm beds!

By the way, I came across this video on YouTube featuring a bunch of these worms in someone’s garden. These look exactly like the ones I’ve been finding around my yard

If you want to be really grossed out, check out this video showing horsehair worms leaving their cricket host:

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    • Tracy M
    • June 6, 2010

    “If you want to be really grossed out, check out this video showing horsehair worms leaving their cricket host:”

    You gave fair warning. What was I thinking?

    • ErickNL
    • June 6, 2010

    Haha, how cool is that. Man, I don’t know what I would have thought if I’d find that on my front porch lol. I am visiting Canada for a few weeks this summer. Going to see if I can find some over in alberta!

    • NG
    • June 7, 2010

    These worms are fine, they’re known as Enchytraeidae (potworms or whiteworms).

    I have a worm cafe wormery & there are a lot of them in the bottom tray which collects liquid. I’ve taken a picture of them for you. Image of the worms may not be clear because they do flail around a bit.

    I’ve also noticed that they are present in other trays of my wormery (most likely due to the high moist conditions/areas of my plastic wormery) & on certain types of high moisture foods, but they haven’t posed as a threat to the worms, springtails or other organisms that I’ve noticed.

    Can’t remember where I found this, but as I’ve mentioned they like really moist conditions, if they clump together in a corner, like a ball, you can use them as bird food, but personally I just leave them or pour them back into another wormery from the collected liquid feed rather than have birds eat them & have a dump in my garden or on me.

    Hope this helps.

    • Bentley
    • June 7, 2010

    Hi NG,
    With all due respect (and I DO appreciate your efforts to help) I have seen countless White Worms (and Enchytraeidae in general) over the years – in my worm bins and in aquatic samples.
    White Worms are in a completely different phylum (Annelida) and are actually fairly closely related to regular earthworms.
    Nematoda and Nematomorpha do not have any segmentation, and they tend to have a rather rigid body in comparison to the softer annelids.

    I have certainly seen some fairly big white worms (pot worms) before, but I can tell you for sure that these are not them.

    • Anna
    • June 7, 2010

    How common are these? (Btw, I could help thinking these look just like Asian rice vermicelli. Oh dear…)

    • Bentley
    • June 7, 2010

    Hi Anna – they can be extremely common in aquatic environments. I don’t think they are all that common on land though. This is the first time I’ve seen them on my property (or anywhere on land for that matter), and I tend to have an eye for little critters. Must be the right combination of conditions this year or something like that. Still trying to figure out what creature they would have hatched out from. We’re not into grasshopper/cricket season yet.

    • Anna
    • June 9, 2010

    Do you have a good worm identification guide you’d recommend?

    • Bentley
    • June 10, 2010

    Hi Anna,
    An ID guide for earthworms, or ‘other’ types of worms?
    I seem to remember there being a decent ID key for earthworms out there – need to look into that.
    As for nematodes et al. I’m not really sure. Undoubtedly a microscope would be needed in order to accurately ID them (down to family/genus/species anyway)

    • Anna
    • June 10, 2010

    I’m trying to identify the assortment I got from another supplier. So far I know I have blue worms, E. fetida, and L. rubellus. There are others too, but I don’t know what they are.

    I did find a reference online for Soil Biology Guide by D. L. Dindal (editor). 1990. Wiley, New York. However, it’s out of print and the only copy I could find was going for $2,400 on, which is out of my price range :).

    • Tina
    • June 10, 2010


    Thanks for posting this! I too saw these worms hanging out enjoying the rain on my bushes here on Whidbey Island. I was thinking how odd it was seeing inch worms moving in the rain and then looked closer. I was rather freaked to see how long these worms were and asked kids not to touch the bushes.. I am glad to know they are more interested in grasshopper/crickets than humans. (visions of roundworms from biology class were going through my head when I saw them) We have heard reports of higher than normal grasshoppers in the area for this summer so maybe this is why I am seeing so many here.

    • allochthon
    • June 11, 2010

    You sure you didn’t just take some pics of spaghetti? 😉 That second pic especially looks like angel hair… How about some marinara sauce?

    • Cindy
    • May 6, 2013


    I found one of these on whipping around on a potted plant last year. I’ve never seen anything like this before. When I first found it I was so afraid it was a raccoon roundworm since we have raccoons roaming through our neighborhood and I’d just read several articles about raccoon latrines and roundworms and how dangerous they are. I was so relieved when I found it matched the description of a Gordian worm, especially since I discovered it next to an area where I’d been having problems with grasshoppers.

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