What Is This Wasp With a 4 Inch Long Thready Tail?

While watching a House Wren hunting among the tall grasses and rushes in an almost dry marsh in Mississauga, I watched as another odd flying predator wobbled into view. This one was some kind of insect. It looked like a wasp, but had an amazingly long tail.

I would guess the tail along was about 4 inches long and thread-thin. It was much longer than the insect’s body. The legs were also unusually long. Given the fairly small wings were located way up on the “shoulders” of the creature, it was not very aerodynamic. In fact, it flew very badly. The long tail also seemed to cause trouble as it bumped into the vegetation.

Photo of Giant Ichneumon Wasp Tail on NaturalCrooksDotCom

I took a few photos although it was a bit too far away to focus on clearly. As I watched, it rose up and moved a few grasses over, then settled again. This repeated several times. I couldn’t tell if it was trying to feed, trying to catch something or trying to lay eggs. I wasn’t even sure exactly what it was.

When I was home, I searched the internet for wasps with long tails. It didn’t take long to find my insect: it was a Giant Ichneumon Wasp. The helpful people at BugGuide.net confirmed it was a Megarhyssa macrurus.

Why Does This Wasp Have an Amazingly Long Tail?

The “tail” that makes it so awkward for a female Giant Ichneumon Wasp to fly is actually an ovipositor. It’s used to lay her eggs.

Photo of Giant Ichneumon Wasp Tail Closeup on NaturalCrooksDotCom

Like a woodpecker, this wasp drills through dead tree trunks to reach the grub-like larvae living deep inside. Unlike a woodpecker, she doesn’t eat them herself: instead she lays her eggs on them and the baby Ichneumons eat them. She also doesn’t drill a hole in the wood with her bill or mouth, instead she drills with the long pipe-like ovipositor!

There are some videos and an interesting written summary of how the Giant Ichneumon Wasp drills down through a dead tree trunk to reach an insect larvae and lay an egg on it at the Nature Documentaries website.

It’s fascinating to think anything as long and delicate looking as this wasp’s ovipositor can actually work its way through wood!

According to the Animal Diversity website of the University of Michigan the wasp lays one egg directly on one larvae of a Pigeon Horntail. To do that she must hear the larvae in the dead tree, then drill down with her ovipositor to reach the horntail. The site says it is not known exactly how the female detects the presence of the larvae: it may hear it or smell it. They also say it can take an hour for her to successfully drill, lay her egg, and pull out, and that she is vulnerable to predators during that time.

Photo of Giant Ichneumon Wasp Closeup On NaturalCrooksDotCom

What Do These Awkward Wasps Eat?

As adults, Giant Ichneumon Wasps don’t seem to eat much. There are some photos though of one of them apparently drinking juice from a grape.

In the larval stage, one wasp feeds externally on one Pigeon Horntail larvae, eventually killing it.

Pigeon Horntails, Tremex columba, are another type of wasp. They are a wood wasp whose grub stage usually lives in dead or dying trees. Trees they live in include beeches, elms, maples, oaks, poplars and apples, according to BugGuide.net. All of those trees grow along the Credit River valley in Mississauga.

Can Ichneumon Wasps Sting?

According to Lloyd Eighme, retired entomologist on the Washington State University Skagit County website, the wasps probably can sting but are not known to do so. The author doubts that most of them could get their sting to penetrate your skin.

The Texas A&M AgriLife Extension website says they could sting if improperly handled but are, in the words of the Hitchhiker’s Guide to the Galaxy, “mostly harmless.”

Other websites say they don’t sting. They are probably correct because they are not saying that they can’t sting only that they generally don’t.

I did not read any comments on any websites from someone claiming to have been stung by one.

Frankly the female flew so awkwardly I can’t imagine why you wouldn’t be able to swat it out of your way before it could even try to sting you, if you were worried. I certainly didn’t feel nervous approaching it as closely as the path would permit.

Keep Your Eyes Open for Strange Insects

I spotted this odd character while waiting for a House Wren to return to its nest with food for its chicks. Had I not been waiting I might never have seen this Ichneumon when it wobbled into view. It served as a good reminder that I need to stay alert and look for new animals on my rambles.


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Have you ever seen such a long-tailed wasp? Was it trying to lay eggs? Please share your sighting with a comment.

108 thoughts on “What Is This Wasp With a 4 Inch Long Thready Tail?

  1. I found these wasp like bugs similar to the one shown.
    it has three whips coming from its rear end. Its primarily black but has a yellow head and legs, it’s wasp like with wings. I noticed one of them drawing it’s whips into a loop and secreting an opaque substance to form a membrane inside the the loop. At the end of the abdomen it forms a bulb 2 wings yellow antenna total length is probably 6″ also rather frail looking. Total body length is about 1 1/2″. It can also open the bulb area and close it between two of its thoracic scales. Can you tell me what the hell it is?

    • Hi,
      I think it may be a Giant Ichneumons or a relative. I see some photos on BugGuide.net that have a strange membrane etc which may be a little bit like what you are describing. Check out
      http://bugguide.net/node/view/21495
      and see if it’s similar.
      There’s also a photo of a dead Ichneumon which has three “tails” at http://forums.anandtech.com/showthread.php?t=2188082 but it’s not identified by type.

      I hope this helps a bit. If you have a photo, I’d suggest you post it to BugGuide.Net and ask for an id. They’re very helpful.

        • They are very strange looking! There are several kinds of these wasps so the colouring will vary and the size and shape can too. Thanks for sharing your sighting!

        • I saw one of them today 10/02/16 laying its egg at the base of a dead tree stump. It was very strang. It looked as if it was ripping its bottom half of its body open while standing on its front leggs doing a hand stand pulsating its butt in and out from where its tore open.

  2. I had one fly into my house this morning in downtown Toronto. I rescued it and returned it outdoors.

    • That was very kind of you! They look quite intimidating with that long ovipositor but really they are helping the trees by keeping the damaging insects in check. Thank you for sharing your sighting.

  3. We spotted this odd big bug last night hovering around our garage light outside. We took pictures of it as we had never seen it before. My mother in law did some searching and determined it to be a giant ichneumon. I had no idea this bug was native to Kansas.

    • Interesting way to find one! I don’t know their range either but I’m glad you got a chance to see one. Since they are harmless they are quite something to look at. Thanks for sharing your sighting!

  4. Eeekl I just found three of these wavering around a dead tree trunk in the backyard. That long taily-thing was inserted in a crack in the trunk and I wondered if they were laying eggs. Evidently so. It’s getting dusky out there so I’ll take a picture when the light is better.
    I thought it would be harder to figure out what they were but when I put “wierd wasp” in the google search box one of the suggestions was “…with a long thread-like tail.” Found what I was looking for.
    Oh, I’m here in Oklahoma City.

    • They are very strange looking and not too appealing. Once you know they’re harmless though they’re actually kind of interesting. Thanks for sharing your sighting!

  5. I’m in Connecticut. I’ve been seeing a wasp (normal looking) flying around the corner of my house lately. This morning I saw one with that crazy-long ovipositor (at first I thought it was carrying a piece of straw, but wasps don’t do that!) and it crawled under a section of house siding.

  6. I just filmed one flying around my garage here in Eastern PA. Scared the bejesus out of me when it flew past the metal I was fixing to tack weld. Looked it up and saw it was harmless. I them out my 12ga. away and helped it find the door out.

  7. Saw one yesterday, very interesting and vividly striking. I thought at first it was a dragonfly with wasp like orange and black bands, but then I saw the long tubeless Overpositor. Had a hard time flying and was on the grass. We have 4 apple trees in our yard so I suppose she was interested in those? We live close to Sandpoint, Idaho.

    • They are very noticeable! I’ve read there are many different kinds of ichneumon wasps so I can’t be sure if the prey was some type of insect inside your apple trees or not, but it’s quite possible. The very long ovipositor is for getting at larvae that are deep inside soemthing, usually a tree. Thanks for sharing your sighting!

  8. I found one on March 12th as I was cutting up dead trees on my property. I live in Lexington SC. Got a 30-second clip of it flopping around.

  9. Found one inside my friends house just now scared the crap out of me so I trapped into a container I’m in the middle of Missouri

  10. Hi! I encountered several of these on a log at the Bad Creek camping area on SC’s Foothills Trail on May 9th. I counted four in all. I watched as two of them expanded their green tail membranes and apparently impregnated host larvae with their eggs. I was unsure of what I was witnessing at the time. They’re quite strange to watch. The membranes are not flat, and they gyre and gimbal rhythmically as the wasp works, like a curled green leaf waving about in a breeze. The wasp’s body is otherwise mostly still. While one of them was working, another seemed especially interested in it and landed to circle it a number of times, antenna dancing. She eventually left. Now I suppose she was scanning the log for the same unfortunate larvae who was about to be parasitized.

  11. One of these BIG wasps flew in my poppop’s car.It was so big I thought it was going to carry me away.I did not know at the time it was not dangerous.My pop pop saved us all he brushed it out of the car.I live in Bucks County

  12. I just took a picture of one on my hosta and what an amazing looking insect. I live in central Northern Missouri.

  13. We live in Papillion NE we saw this creepy wasp with a 5 inch stinger it was on our window and we through shoes at it and it fell down and we thought it was dead so we opened the door but it was actually ALIVE ! And flew out.

    • As it turned out, it’s good that it was alive (once it left!) since it couldn’t do you any harm. But I understand not wanting to share your house with it! Thanks for sharing your sighting.

  14. Found this wasp with the long tail crawling over some cut down tree wood that I will be stacking for fire wood.
    It seemed to be searching for something.
    After looking it up, it is indeed a Giant Ichneumon Wasp. After reading about how it searches for places to lay it’s eggs with it’s long ovipositor, that’s what it seemed to be doing on the wood pile, searching for holes or cracks between the bark. The first one I’ve ever seen living my 56 years in Maryland.

    • They are quite interesting to see if you can get past the look of them. If it does find something to lay its eggs in it will save some of your wood for the stove, so it’s actually helpful. Thanks for sharing your sighting!

  15. I just found one of these in my backyard for the first time in my life. I live in the Matsu Valley outside of Anchorage Alaska. This thing was massive, the size of the small birds that hang out in the backyard. Just came in a googled it because it was so interesting. I haven’t seen any comments about people finding them here in Alaska yet either.

  16. I saw one of these giant wasps in my yard, it was trying to climb a garbage bin with no success. After taking pictures I held out a stick so it could get on and I lifted it to the top. It flew away very badly, it was very slow as well. After researching it I’m very happy I didn’t kill it!

  17. I saw one in my garden this morning. There is a maple bush abt 20 feet away. Thanks to your pics for a positive id and interesting post. A friend put a link on my FB when I posted a picture I took. I was able to run into the house and grab the cam and go back out to find her still resting on the leaf.(eastern Ontario)

  18. There is one in my sunroom right now and I was scared to go back in there but I’m ok now that I know they are harmless. I will open the door and hope it flys away. I’m in Atlanta Georgia

  19. Just had one in my house tonight. I’ve never seen anything like this before. Unfortunately, my daughter swatted at it and , it did not make it.

    • Well at least you’ll know for the next time, although hopefully that will just be one outside as I’m sure you don’t need any more inside, ever! Thanks for sharing your sighting.

  20. Working in my garden today and heard a loud buzzing so I had to see what it was. It was one of these guys/girls but for some reason it was stuck in the raspberry canes and couldn’t get free. I found a piece of dry grass, a long piece, and helped it get loose. Last I saw it was headed east. I have lived in Colorado 40 years and I have never seen one until today.

  21. My oldest son and I saw one of these flying behind the car as we were getting all of my boys in. It was HUGE! The one we saw was more black and yellow with yellow tufts coming from it’s head. When we looked it up, we came across this site. It’s exactly what we saw. The stinger was approximately 5 inches and the body was about 2 1/2 inches. By the way, we live near Bangor, Maine!! Not sure it should have been this far North! :)

    • You definitely saw a giant ichneumon. There are quite a few varieties and I won’t claim to be an expert on the various types. I live in Ontario so they do come quite far north. Thanks for sharing your sighting!

  22. One in my sunroom in Fayetteville nc. Creeped me out and so glad the wife and kids weren’t home. Would’ve scared them senseless lol

  23. One has been on my window a few hours. I’m in South Central PA. It’s very humid right now, and dark. She seems to be going toward the light in the house. I’m unsure what to do with her. Will she drill the wood in my window?

    • No, she won’t drill into wood unless she’s aiming for an insect already inside that wood. It’s unlikely you have any wood borer larvae in your windowsill, so she’s probably just sheltering and maybe interested in the light. Thanks for sharing your sighting!

  24. I have never seen this bug before and was scared to death of it. I got my sons to get it off of my screen and found out it was actually pretty clumsy and docile.
    Once we found out what it was we placed her in the deeper part of the woods near our house.

  25. We have had a few of these at our work (Alliston, ON) in the last week or so. Do you think something has changed that we are seeing these for the first time?

    • Yes but not anything huge. I think somewhere in your neighbourhood there is a dead or dying tree that has the type of insect larvae inside it that these wasps need for their young to eat. I don’t think it’s a problem though; it’s just natural. I’m sure they are a bit worrying to see the first time, though, until you realize they are fine. Thanks for sharing your sighting!

  26. I have found one my son knocked down its the same as in the picture . found it in Ohio ! She has 3 long tail things beautiful Creature
    I would post pics but I don’t know if I can .

    • Unfortunately there’s no way to share your photos here. I’m glad you got a good look at one–they’re quite interesting once you know they are safe. Thanks for sharing your sighting!

    • I don’t have a good answer for you, sorry. If it moves near the doorway, you could probably flap it out with a newspaper. Will it land on a newspaper so you could carry it out? They don’t sting or bite. I’ll hope something works out, and thanks for sharing your sighting, even though I’m sure you wish it had landed on the OUTside of the screen.

  27. We have just noticed a group of these wasps drilling into a dying maple tree. (About 10 of them together). We had never seen such a thing so thanks to “google” We were able to iidentify them very easily. They are creepy looking but glad to read they are harmless.
    We live in Denver, CO!

    • They are bizarre to look at but they are helping control other insect populations so they have a valuable role to play. Thanks for sharing your sighting!

  28. Just had one flying around the window in my building, trying to get out. Scared the crap out of me and my girls. I caught it in one if those clear plastic take out containers and looked it up to see what it was. Now that I know it’s harmless, I took it outside and let it go by a dying elm tree. That thing was weird. Had a 3 to 4 inch long ovipositor, which at first we thought was a stinger.

  29. I’ve been stung twice by these stinking things. I think they have some sort of vendetta against me because theyre always in my house and room. In fact my brother just killed one now that was outside my bedroom. I think they hate me because I killed one of the ones that stung me years ago haha

    • I’m sorry to hear some type of wasp is after you! I doubt it was exactly this kind, though, as they are not reported to have stung anyone. They are very slow, clumsy flyers which would make them easy to swat away before they could land and sting. I hope that whatever kind is after you gives up, though, and you have my sympathy!

  30. We saw one today in Independence MO. Long tails and brown with some yellow. First time we have seen them around here.

  31. I suppose there are different types of this species. The one I had in my house had a split tail several inches long. I rolled up a paper towel making a tube and laid it down for it to crawl into and it obliged very nicely! I then pinched the paper towel ends shut and carried it outside to my decorative grass. I hope it can find enough bad bugs to eat there!

    • Yes, this group of wasps has many varieties. Thank you for saving your type–they fill an important role in keeping other insects in check. And thank you for sharing your sighting!

  32. 7-27-17 Missouri While sitting in garage late last night one flew right into the light sitting right beside me. First time I have ever seen anything like it

  33. Found this site while googling this particular bug. We found this girl flying in our garage in Edgerton, Ohio, so not just in the Credit River valley in Mississauga!

  34. I saw one on the side of my office building window in Ottawa, Canada in early July! I used this page to identify it.

  35. I saw one in my friends garage it is trapped in the garage door opener we all freeked out my friends 5 year old sister started crying we were having fun playing floor is lava and saw it We live in South Caralina

  36. I live in Delaware one of these flew onto my screened in porch last week. I have lived here many years and have never seen one before. But our property is surrounded by woods. very strange bug .

  37. Hi! I had one sitting on a nearby flower, cleaning its antennas/antennae. I was a bit apprehensive about getting close when I saw the “stinger”, longer then her body. Thanks for telling me that it is an ovipositer. These ladies certainly have a strong urge to to keep their species alive.
    Thanks for your info. Fran from Goulais River, north of Sault Ste. Marie, Ontario

  38. Haha we have them around here – in fact one was just by me, and my reply was “ew WTH is that” lmao. Off to Google I went and I found you! Well at least I know what it is!

  39. It was on my Front Door tonight~~ and I thought ,”Whhhhaaaaaatttttt??”

  40. At 2:30 in Harrison Michigan in my garage this one has more of a yellowish orange head and legs, more like a yellow jacket

  41. I have actually been “stung” (or maybe but) by a male of this species. I thought it was a harmless bug and in my super soft hearted attempt to save it without having to kill it, as it was inside my house, it stung my finger. The pain was intense and it left a red welp for a few days. Definitely won’t mess with them again!

    • I’m sorry to hear you were injured by a wasp. It could have been a bite if it was a male–only females have stings because the sting is a modification of the ovipositor, from what I’ve read. It may also have been some sort of “mimic” creature that looked like an ichneumon but was something else. Either way, it doesn’t seem fair you got hurt trying to be kind!

  42. One of these has been flying around my bedroom for a few days. I live in Seattle and have seen a few here over the 12 years I have been here. Since it can’t seem to find its way out, I will capture it and put it out the backyard. Thanks for the information you shared.

  43. We live in Central Arizona. Last night is the first time we’ve ever seen one of these in 23 years. It was flying around the garage light so I turned it off and put the outside garage lights on. It went out there and I got few pics and video. I found this site when I Google it. I enjoyed reading about it, and all the comments. Thanks for all the info. Interesting.

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