“Alien Worm Circles”

By Jim White, Associate Director, Land and Biodiversity

I have always enjoyed answering questions about wildlife and take a bit of pride in being able to come up with answers quickly. However, every now and then there are questions that are real stumpers. These questions are always the most fun to work on and often require communication with other naturalists, flipping through old field guides, and of course searching the web.

One such question turned up the other day. A friend of mine called me when he and a few of his neighbors discovered an interesting scene on the neighborhood sidewalk. My friend described it as several groups of worm-like things forming a rope and walking en masse in a clockwise circle. The ropes were several “worms” thick and joined head to tail. He was speculating (in jest) that they were an alien life form. To be honest I was wondering if he might be right. Luckily, one of the neighbors, Paul Dreyfus had a digital camera and was able to take a few photos and send them to me. I waited in anticipation, figuring that once I saw the photos I would know exactly what the “worms” were. But noooooo! Although I could tell that they were insect larva I had no idea what kind.

Strange insect larvae walking in a circle on a sidewalk.  Photo by Paul Dreyfus.
Strange insect larvae walking in a circle on a sidewalk. Photo by Paul Dreyfus.

I decided to ask Richard Smith a well-versed entomologist that I know. He was also stumped but did some web searching of his own and found our answer in a photo on an obscure garden listserve. Sure enough the photo was a match – the “aliens” were the larvae of a species of Dark-winged Fungus Gnats (family Sciaridae). As their common name implies, the larvae of these small flies (order Diptera) feed on fungus, but they also eat the root hairs of many plants. Some species are known pests of mushroom cultivation and greenhouse operations.

Dark-winged Fungus Gnats close-up.  Photo by Paul Dreyfus.
Dark-winged Fungus Gnats close-up. Photo by Paul Dreyfus.

So with the identification in hand I set out to find out all I could about these intriguing insects. I figured a few minutes on the web would give me as much information as I wanted on the little guys. Wrong again. So far I have only found out the following:
• The larvae often live in large congregations and from time to time move en masse to new locations.
• In Europe there are several species of Dark-winged Fungus Gnats, especially the army worm Sciara militaris, that migrate in processions up to ten meters long, containing thousands of individuals.
• The circles apparently form when the leading larvae mistakenly hooks up with the larvae at the tail of the “rope”, forming an endless loop.
Many questions remain about why and where the larval migrations occur and how frequently the circles form. I will keep searching for these answers and report my findings (if any) in another blog. Meanwhile, please contact me if you’ve seen, or have additional information about, these “alien worm circles”.

163 thoughts on ““Alien Worm Circles””

  1. Went out to the barn this afternoon and noticed a huge circle of what I first thought were twigs washed/blown up in a huge spiral or circle. Upon closer examination, It was a circle of worms all crawling counterclockwise around an eight or 10 inch diameter bare spot on the ground. The bulk of the ring was about 20 feet in diameter, but there were significant numbers of worms crawling round and round in about a 35 foot diameter circle. The worms appeared to be about 4 to 6 inches long and looked like a common fishing worm – not a nightcrawler.

    I have pictures. “Worms” look like common red worms only are dark gray/brown.

    I googled it but couldn’t find any explanation.

  2. I encountered this today, although not in circle form. I video taped it from my phone. If interested in see the video. Send my an email address

  3. I looked out on the patio this morning, saw what appeared to be two foot long stripes of diarrhea left by a sick possum or cat. A few minutes later, it’s gone, but a couple of odd shaped areas show up not far from it. Closer looks shows they’re teaming with small worms about 3/8’s inch long. They’re in shapes about the size of the palm of your hand, with the whole shape moving.

    Looks like a quick spray of Raid Ant & Roach knocks them out, but what the heck are they?

    A lot of references to gnat larvae tells me I might need to re-spray with bug killer I put down for grubs and hope that gets them.

  4. I noticed a similar moving circle of “somethings” on my patio this morning here in eastern Oklahoma. I’ve never seen anything like it. Creepy! When I googled, this is where it led me. Whew! I too thought maybe we were being invaded. 😉 Thanks for the info.

  5. Noticed bout a 4″ circle this am.
    South end od Toledo Bend Lake, Texas Side, North Newton county Texas.
    Sprayed with roach & spider spray…..killed them

  6. Joe Sebastiani

    Again, these are harmless insects and there is no need to kill them. We encourage people to limit the use of toxic chemicals, and to restrain themselves from using it on things that are harmless, such as these insects described in the blog.

  7. I found the four inch bracelet on my patio this a.m. in south western Pennsylvania. I started to pick it up and it started moving!
    scooped the rope thing up with cardboard and put it into a plastic bag and stomped on it.

  8. Hello, found a circle on my sidewalk this am. About 6″ round. Crawling counterclockwise. I live in Central PA. So weird!

  9. Today on sidewalk at office in Fort Collins, CO. Several of them. Thanks for posting this, we were all perplexed!

  10. I just found a 5 inch circle of these creatures on the cement by my garage door. Location: Near Allentown, PA.

  11. We had a 7 inch circle on our front walk this evening. Ellicott City, MD. Never seen such a thing. Where do they come from??

  12. I seen them for the first time last night and recorder them…. I too thought it was some Alien form email me for the video

  13. I live in MD and thought my daughter dropped a bracelet…it was dark out so I went to pick it up and realized it was slimy and wasn’t a bracelet. I put a light on it and realized it was about a 5″ diameter ring of these worms so I filmed it…it was actually pretty amazing.

  14. My husband discovered a circle of worms just like the photos posted on our downstairs patio this morning. Glad to find this post and glad to hear what they are and that they are harmless. I’ve noticed the location of everyone posting and realize these particular worms are nationwide and not indicative to one area of the country. I’ve never seen these before.

  15. Marcelle Joubert

    I found a circle of worms this morning on the driveway The circle was moving and I am interested to read that others have had similar discoveries

  16. Lilly Albornoz

    Columbia SC. My parents took pictures of some strange bugs moving in circles. There were three. They were repulsive. I saw the pictures and I can’t take that out of my head. I think I have a phobia for repetitive patterns… Because this moving circles are REPULSIVE. My mother thought we were being invade. She boiled water and dumped it all over them. Yuck!

  17. Dededidi@comcast.net

    I have pictures and video. So glad to finally find out what they are! I feared they were termites. They formed a long rope like line.

  18. Jeremy Pelham

    Found a circle of them in my driveway this morning. Really surprised me. I’ve never seen or heard of this.

  19. The circle of them I had on my driveway resembled an ancient symbol, lol I’ve got great video. Unfortunately they kept heading into the driveway rather than out and fried on the hot concrete…

  20. A link to my video of it won’t post here, but there were a couple lines of these crossing from the grass onto our driveway this morning in south-central PA. A couple friends thought they were Tent Caterpillars but after seeing these here and looking up other posts about Dark-winged Fungus Gnat larvae, it looks like that’s what they were.

  21. Our patio had several circles of these larva this morning, and a line moving up our table leg. it was very creepy. So glad I found this web site. We are on eastern long island. What is the way to prevent them from returning? Could they be coming from a potted plant on the patio?


    We have them both on our patios and in driveways in Blue Point, NY. Can you tell me what is the cause and how to get rid of them? We have a lot of new construction going on here in our community and thought their nesting was disturbed.

  23. Found a worm circle just like the picture this morning in Waverly, OH, about 60 miles south of Columbus. The strangest thing I have ever seen. Took a video and have shown it to a few people, no one has seen anything like this.

  24. This happened to us about 10 years ago at the home we were living at. I had opened the door for my dog to go potty. She stopped in her tracks at the door and ran and hid under the bed. I went to see what was wrong and there in our driveway up to our front door were these circles of worms. They were shaped in the circle as a donut. Not climbing in nor out but going in a circle. It looked like some “thing” had walked from our driveway to our front door and dropped them with each step walking on two feet. We were terrified!! I had no camera to take pictures which I wish I had. It looked as though the devil had walked right up to our door! My husband rinsed them off and when we looked, they were all gone!! Our neighbor was a demonologist and I think she brought something there. When she moved, it never happened again. To this day, it scares me to think,about it.

  25. I have had these show up on my driveway the past 4 mornings. Each morning when I get up there are anywhere from 8-10 piles of them moving around. The are dying in the heat as it is reaching 90 degrees. But the next morning there are more piles all over my driveway. The majority of the piles tend to be under my car in the morning but not all of them. So very strange. What do you think?

  26. I saw a ring of worms on my front walk way this morning. We live on the north shore of Boston. An hour later, they formed a line and traveled westwards. So, I agree with the hypothesis that the lead worm lost its purpose and identity, thus forming an aimless traveling pattern.

  27. We just found a circle on our sidewalk in Southwestern, PA. I was so freaked out. Thanks for the information.

  28. Saw these on my sidewalk today. What a gross sight. I guess September must be the month for them. I hope to never see it again.

  29. Found a circle this morning. Pittsburgh pa! So gross. It’s still there circling around & around

  30. Robert and Margaret Henderson

    This is Robert and Margaret Henderson from Peebles Ohio and we just encountered one of these worm circles strangest thing!

  31. Saw a circle for the first time last night. They were circling my sidewalk. What a wacky sight for our little Schaefferstown,Pa.

  32. I have one on my sidewalk behind my house right now. I videoed it when I first spotted it and went back several times to take still photos. When I first saw it, it looked like something woven, maybe a coaster, but then I realized there was movement and looked closer thinking ants were crawling on it. But it was way worse! Very creepy, as others have said. Over time it went from that small woven appearance to a much bigger, much thinner ring, and eventually moved off to the edge of the sidewalk. It’s dark now, so I don’t know if it’s still there. I can send you the video and photos if you’re interested. Thanks for the info!!

  33. Just found this in my walkway! What is it and where do they come from? So creepy! It’s was a large circle as well.

  34. Found these worms 2 days ago in southeast Ohio. We see them in the morning. I think they are moving from the yard to the flowerbed. Not always in a circle. Just a blob moving in one direction. Will they hurt plants?

  35. How funny that I am searching for this oddity that I saw in my driveway and there is a blog for it. Just ewwww! Not knowing what they were and not having time to research it, I got out the vinegar and dumped it on the circle of aliens in my driveway. I did notice 1 much larger and white larva next to the circle. There were also a few other patches of these larvae. The only reason I noticed this, was that my husband just pulled out of the driveway. The driveway was wet from rain, but not where the car was parked. I saw dark spots and thought he might have had an oil leak. I went to check. Nope, just creepy crawlers.

  36. I have millions of these things!!! In globs, in circles, in lines. I took many pictures and videos never seen anything like it!!! I’d love to send the pictures and videos!! Thanks, Jamie

  37. Saw a ring of these and a rope-like figure of these for the first time ever today on our back concrete patio in Bethel, Ohio (east of Cincinnati).

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