Thursday, June 11, 2009

Giant ichneumon wasps

Prowling around a pile of cut logs near my temporary residence in South Deerfield, Massachusetts on the evening of June second, I almost literally stumbled upon one of the most spectacular wasps on the continent. Female giant ichneumon wasps in the genus Megarhyssa may look menacing, wielding a whip-like “tail” that can exceed their own body length, but they cannot sting and in fact are quite shy, easily startled by sudden movements. It is a pity that people are often so alarmed by these insects, as they have an extraordinary life cycle.

That long, streaming appendage at the end of her abdomen is not a stinger, as the uninitiated tend to assume, but an egg-laying organ called an ovipositor. What she does with it is truly remarkable. She is seeking the grubs of another stingless wasp, the “pigeon horntail,” Tremex columba. Horntail grubs bore in the solid wood of dead, dying, or severely-weakened trees. Along comes a giant ichneumon wasp. The ichneumon somehow “divines” the location of the horntail grub inside the tree or log, then arches her back to pull her ovipositor into position to drill into the wood to reach the horntail grub. Whether she actually penetrates the solid wood, or winds her thread-like organ through existing cracks and crevices is still a mystery, but she manages to deliver her nearly fluid egg to its target host. The ovipositor is actually three filaments: two form a sheath for the actual ovipositor, bracing the animal’s abdomen and allowing the ovipositor to work smoothly without undo bowing.

Once her mission is accomplished, and her egg is attached to the horntail grub, the adult female ichneumon slowly withdraws her ovipositor and begins the process over again, walking the log or tree with antennae outstretched like divining rods.

Meanwhile, her egg eventually hatches, and the larval ichneumon attaches to the exterior of the horntail grub. It will wait patiently for its host to reach a large, nearly mature size, then begin consuming it. The horntail grub is doomed, destined to yield an adult ichneumon rather than a horntail wasp.

Look for giant ichneumons around dead or dying trees at all times of the day. While ovipositing, females are vulnerable, and one can sometimes see where a wasp was taken by a predator. A hair-like filament protruding from a log is all that is left of the wasp in such cases.

Male giant ichneumons like this one can also indicate the presence of females as they vie for mating opportunities. Note that they almost resemble a different species of wasp! Many males may gather at the site where a female is about to emerge. It is quite a spectacle.

Four species of giant ichneumons collectively occur over most of North America. The ones shown here are probably the species Megarhyssa macrurus. Females can vary considerably in size depending on the size of their host as larval wasps. Smaller individuals tend to have reduced spotting on the wings (or no spots at all). Enjoy looking for these insects and observing their amazing behavior.

91 comments:

  1. Great article Eric, beautiful pics too. You are so right, these are amazing creatures. I had one in my yard last year that deposited eggs into an old stump of a long dead maple tree.

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  2. Wow. I would love to find one of these, although it would probably give me a start at first!

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  3. I have never seen the giant ichneumon, but I have seen the horntail, and they can be startling as well!

    Nice post.

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  4. What's going on with the membrane at the end of her abdomen? I noted this in your Kaufman Insects, but thought it was a bad crop job in that photo, that it was background betweeen the filaments of the ovipositor. However, looking at the full-size image of your second photo here, I see it's actually a membrane. It almost looks like the tip of her abdomen separates and folds open.

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  5. Seabrooke: I suspect it is simply a highly-elastic intersegmental membrane. She (the wasp) needs to be able to brace herself to drive her ovipositor into the wood, but also needs to be able to have it trail behind her when not in use. This flexible membrane allows her to do both. It does look fragile, I agree.

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  6. We recently had a tree removed and noticed these on the remaining stump over the weekend. There were about 10 of them. They seem to come out early in the morning and at dusk. Do we need to worry about them depositing their eggs into our stump? What are we to expect when they hatch?

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  7. With all due respect, did you even read this entry? It explains everything. Thank you.

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  8. Wow! I saw my first Ichneumon not long ago and was amazed at how large this female is! Just so you know, I am going to take your "they cannot sting" words to heart and see if I can't have one sit on my hand if I ever see one. A neat party trick!

    Great post!

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  9. As I gathered from your labels for this entry, I'm very glad to hear that they're harmless, because I had one fly right at my face at the mini-golf where I worked today! I hit the deck just in time; it flew a few circles over my head and then flew away, but not before I noticed it's large size and the long "tail" trailing behind it, leaving me wondering what the heck had nearly flown into my face. I'm usually not afraid of bugs, but I think my alarm was justified in this case.

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  10. Hi Eric, thanks for the explanation (never seen them before today, in SE Mass). I just stumbled upon 4 pairs of these on a living tree in my backyard. Would it be safe to assume that this tree doesn't have much life left in it (a maple, it seems fine, plenty of leaves on it)?

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  12. Thanks so much for this post! I was working in downtown Portland, Maine today when one flew right into the shop. This thing was HUGE! I've never seen anything like it. It took a little while to find its way back out.

    I got a great picture, if you're interested, but I'm not sure of the best way to share the photo.

    By the way, I deleted my last comment because of some grammar errors... :-) I'm still learning how to navigate the blogosphere.

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  13. Eric, thanks for the photos and information, now I know what I was looking at. Last night a GIANT Ichneumon (Wasp) showed up at my porch light in Edgewater, MD. I watched it rip through spider webs before taking an all night break at my front door. Nice to know that it does not sting...because my kids thought it was hunting them, so they were refusing to go to camp!!

    What a beautiful wasp!

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  14. Brilliant job on the article! One just landed on our window and scared my wife. I had never seen one before but after reading this article I find them interesting. Thanks!

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  15. Sat and watched a small group of these black wasps today. Amazing creature.

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  16. Thanks for the info. I took a picture of this "mysterious" bug and found the info on your site.

    Wow! They're really cool :)

    Sandie lee

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  17. Hi Eric;

    I took a pic of another weird bug in my yard. It has almost shiny balck wings and a bright orange and blue head with long antennas. Would you have a guess of what it may be?

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  18. Came across this article after having found one these beautifully weird creatures. I had no idea what it was before reading this article. Excellent write up! Thanks for sharing!

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  19. Great info, thanks... I have pictures of a female laying eggs in my wood pile here on the shoreline in Connecticut from last summer. I almost fell over myself trying to get the camera when I first saw her.I had no idea what it was to begin with until I posted pictures on Facebook and a friend told me what it was. I feel very fortunate to have seen this process and will be much more aware this summer. :)

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  20. I read the article, but still have a question. I was getting ready to burn a brush pile with a an old tree trunk at the bottom and ran across a bunch of these. Are they a beneficial insect to a garden? Are they rare? I really need to get the brush pile out of there but am hesitant to burn these insects out. How long will it take for the eggs to hatch and leave?

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  21. No, they are not rare. My question is how do you know that is what is in your log? They can't be adults yet, so I don't know how you arrived at your identification.

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  22. I found one of these hanging around outside our apartment (NW Indiana), and I was surprised to read that they are quite shy. This one hung out for hours right next to the sliding glass door we use several times a day. I took pictures but they didn't turn out that great because I was afraid to get too close. Now I know if I see one again I don't need to be afraid of it!

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  23. Thanks for the informative post. There is one flying around our chandelier right now. Your article provided a great Homeschool moment for my kids!

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  24. Ughh. A bunch of them killed off my maple tree this summer.

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  25. If you had actually read the blog you would know that these wasps do *not* kill trees! They kill the horntail woodwasps that occasionally *can* hasten the death of a weakened tree. Thanks for visiting.

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  26. I just smashed one of these evil-looking bastards with a hammer. It did not look harmless and was sure that "tail" was some kind of needle. And I live on the south island of New Zealand! Invasive? Thanks for the info. Will not kill the next one I see.

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  27. Fallon: Interesting. I see that Megarhyssa nortoni was introduced to New Zealand intentionally, sometime after 1962, to battle a true invasive: Sirex noctilio. So, the ichneumon is *still* a "good" wasp, just not a native one.

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  28. Hi Eric, great blog! I found a female nortoni in my church tonight and in the process of researching it read that the hornwood wasp introduces a fungus along with its egg in order to help hide the hornwood larvae when it hatches. The Megarhyssa can apparently use this fungus help it locate the location of an egg. Have you heard anything about this?

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  29. Thank you for the compliment, Ivan! This is apparently my most popular post *ever*....I was under the impression the fungus was to help soften the wood so the larval horntail can more easily chew its way through the tree. It does seem logical that the ichneumon might use the odor of the fungus to find a horntail grub. Very interesting, thank you for sharing!

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  30. I just seen one the other day & I ain't gonna lie, it scared the sh*t outta me!! But im glad to know they dont sting!

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  31. After my first encounter with one of these, I feared that all I had been taught about the good and holy was a ruse and that no loving god would set me adrift on a rock in space with them. You've restored my faith.

    They've been attracted to grubs in logs on my patio from a dying silver maple. Pretty amazing that they can find them. Sadly, I vaporized a couple with my air gun before reading your post. Thanks for the education.

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  32. Thank you for the compliments, MLaker, and for sharing your own story.

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  33. I found one flying like mad in my garage and had never seen anything like it before. I guess it lives above the light fixture to stay warm.
    It scared the crap out of me and needless to say I don't like going through the garage anymore..lol

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  34. Wow, I can't believe I'm still getting comments on this one particular post. Thank you for sharing your stories, all of you!

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  35. My 3 year-old nicknamed "Dirt Girl" because of her love for the outdoors found one of these 3 days ago. We put it into a jar and observed it. I was quite certain it was a wasp and it worried me that she found it. After reading your post I am relieved that they can't sting. Very cool info you provided! Thanks!!

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  36. Replies
    1. I have taken a picture of one, at least I think that is what it is since I have read the posts and looked at a few pictures. First time I have ever seen anything like this in Maine and was very concerned about another new bug being introduced here. Can you tell me how long they have been here and why or how they came about. Sure never saw any for the first 50 plus years of my life and have worked and lived in the woods for most of those years.

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    2. I just recently saw and took a couple pictures of one of these (I think), but don't know how to send the picture that I took. Am grateful for the info you have provided but also wondering how long they have been around (in Maine), since I am 57 y/o and have lived and worked in the woods for most of my life without seeing anyting like this until about 3 years ago. Any info as to why or how they came about here and when they arrived as well as from where? Would appreciate all the info I can get for my own peace of mind. Thanks so much.

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  37. These insects are native to North America, so they didn't come from anywhere else. I guarantee you they are not at all uncommon, but you have to be in the right place at the right time to find them (and be looking at a lot of dead trees and logs). They don't sting....Please read the blog post, it explains most everything. Thank you.

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  38. My husband and I were sitting in the garage tonight and one of these flew in. Seriously freaked us out. Thankfully we are of the "we leave it alone, it will leave us alone" breed. We actually decided it looked cool and snapped a couple of pics from our phones. Meanwhile our ever inquisitive 11yr old already had it looked up on the internet. So here I am. Thanks for the info and the pics!

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  39. One got stuck in between my window & screen and scared me half to death wondering what this creepy "dangerous" insect was! It had found a spot where the screen was tore & I was relieved that I didn't have my window open or I would have been tempted to stay with a friend until someone got it out of my house! Glad I found your article. My son wants to jar it and take into show n tell at school. If he does, he can use your info!

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  40. Well i caught one ... its nuts , at first i was like what the hell is this but then i googled it and found out to make sure it wasnt deadly before i pursued to cathch it

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  41. Eric,
    Thanks for your time and info on this amazing critter.
    I recently "found" them in my own backyard (Delaware, East coast US) and had never seen one before.
    They are a fascinating creature. I sat for a couple of hours watching as many females of different sizes gathered around a stump to deposit their eggs.
    Not knowing, until now, the exact process of their egg laying procedures, your information makes perfect sense now.
    I captured a few images (150 to be exact LOL) and plan on taking a video within the next couple of days when the weather is clear enough. (Threat of rain is keeping me from setting up the camera.)
    Here are the images if you're interested in viewing.
    Since they were shot "in a hurry", some are a little out of focus.
    https://plus.google.com/u/0/photos/112599029888747086098/albums/5783192455279538625

    Thanks again for the information. Nice to know!
    - Mike

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    1. Thank you for sharing your own observations, Mike! I'll take a look at your images soon.

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  42. We've had two so far John killed them both they're kinda sketchy. Can the males sting? Would it have any lethality?

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    1. I don't know how much clearer I can be in the post itself: They do NOT sting! This is the kind of ignorance I am out to eradicate, and I am explicit, and people still don't believe me?

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  43. I hate to argue with you, but one of these, "and I killed it afterwards, and double checked my images," stung me twice in less than 2 seconds on my forearm today as I was hanging plastic on my front porch. I saw it batting against the plastic along with some gnats and such, and just went about my business with the staple gun. I ran my arm up right beside it and must have brushed into it, because I immediately got stung. Unless there is another wasp looking really long tailed flying stinger in southern Georgia, this is what stung me. I am no expert, but maybe I got my images confused. Is there another wasp that looks very close to this one that does sting?

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    1. It might have *pricked* you, but it didn't sting you. Stingers are connected to venom glands, so a sting injects venom into the wound. I guarantee you these wasps are not venomous. Again, if you can *see* a "stinger," then it is *not* a stinger. Stingers are always retracted into the insect's abdomen until they are deployed. Sorry about your experience, though, and hope you are fine.

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  44. My co works and I caught one in the summer of 2012. I have videos and pics. Im in Tacoma washington.

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    1. Feel free to share a link to those, Justin.

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  45. Have one on my living room ceiling right now as I type this message in our southern Illinois home. Scared us but your article put our fears to rest. Trying to figure out how to safely get this girl back outside. Thank you for the informative post and pictures!

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    1. Glad to hear I could help, Megan! Thank you for sharing your story; and for your tolerant attitude :-)

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  46. My first experience with one was neat! It was just hanging out on a fence and I had spotted it from a few feet back. Some older man told me it was a "cicada killer" lol but i bet he said it since he lacked the knowledge. Beautiful insects! Thank you for sharing this information with us.

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    1. Thank you for sharing your story; and for the compliments.

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  47. Are they common in Colorado?? I have never seen one before. But the one I saw this afternoon was beautiful. Amazing creatures.

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    1. They are more typical of deciduous forests, so no, they are not common here....or are at the least harder to find, harder to see.

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  48. Since I'm allergic to bee's a thought Holy Mother of God when I saw this thing. My husband trapped her in the window between the screen and posted a sign not to open. Then I killed her. Poor girl, wish I had looked her up sooner. Very relieved that she isn't going to stab me to death with those 3 long tail spikes. Whew. Is it safe to assume that there may be a few more fluttering around? We took down an old tree last year and we have a large maple in the back. Could the combination be attracting her? (Edison, NJ)

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    1. Rene: Giant ichneumon wasps are ONLY going to be drawn to dead, dying, or weakened trees already infested by horntail woodwasps. If one of those trees fits the bill, you may see more of these wasps.

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  49. Thank you so much for your photo and post. My daughter and I spotted what turned out to be a male, we were intrigued and followed him ... he led us to a female laying eggs (I thought it was a mating dance). We watched for awhile, taking tons of photos and enjoying the amazing process. I showed the pics to every local naturalist I know and no one could ID them. So I turned to the internet and was so pleased to be able to identify them and learn that they are not only beautiful but also have a fascinating life cycle! Thank you for all of this! But one more thing... do they sting? just kidding!!! we did read the post and weren't worried anyway ;)

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    1. Amy, you made my day! Thank you for the compliments, and for sharing your story here. This is why I do the blog, to get a conversation going :-)

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  50. Hi Bug Eric,
    I am from Maine. I saw this wasp and said to my mother what it would be. At first, thought it was a cross breed of a dragonfly and then I found your sight. I have seen two of them. Both Females and one was crawling up my leg and I didn't feel it or get stung. My uncle noticed it and I brushed her off my leg. Little creepy at first, but fascinating in another respect.
    Would never thought it would be a wasp. Thank you for your info.

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    1. You're welcome; and thank you for sharing your story!

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  51. My family just saw a couple of these at work on a dead maple tree in my parents' yard in Manitoba. The bright green disk coming out the tail of the insect is amazing, and we saw it happen a couple of times! https://www.dropbox.com/l/iLPXesxDrUeOOA0xHRXRLa I'd love to know more about that, but I haven't been able to find much info about it. Is it part of the mating ritual, or the egg-laying process? It seems extensive!
    Thanks for all the info, in your original post and in your replies - gives me a good understanding of these amazingly bizarre-looking creatures!!

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    1. Daniel, thank you for the compliments and the link to the video you shot....The "disk" is a delicate membrane that holds the ovipositor and abdomen together during the contortions necessary for the wasp to insert her eggs.

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  52. I posted a link to a high quality video of the bug in action here in eau Claire, wi

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  53. Hi Bugeric and Brandon,

    This may be the post that goes on and on and on...! I just found it after seeing my first ever specimen land on our sunroom window. I barely had time to splutter tea, say holy .... and tell my husband to turn around, and it was gone. Thanks to you both, I was able to learn what it was and get a better look. Writing from Wakefield, Quebec

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  54. Found this one yesterday in SW Missouri.

    https://www.facebook.com/photo.php?v=716259948389030&set=o.118150804885025&type=2&theater

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    1. Oh, wow! Great video of a female Megarhyssa atra that has really become "immersed" in her work. I did not know the ovipositor could be deployed quite like that, but sure looks like the case here. Nice find, Jon, thanks for sharing!

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  55. Tarrytown NY, saw this intimidating wasp on my tree yesterday. We took video and pictures in spite of our fear that it was some type of scorpion spawn. Unfortunately I thought it was depositing its evil eggs into my tree and I did not want to battle a swarm of these insects all summer, so I sprayed it with Ortho. I feel slightly better admitting my transgressions on this blog. Next time I will consult your site first before I resort to hasty measures.

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    1. Thank you for sharing your experience.

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    2. To follow up, I do see new baby wasps and one large one with the funky tail.

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    3. A "baby" wasp would be a larva, concealed in the wood of a tree in this case. The wasps without tails are likely males (see image in the blog post).

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  56. Tarrytown NY. I witnessed one of these creatures on my tree yesterday. At first glance I thought it was a scorpion. I took great pictures and video despite my fear. Unfortunately I thought it was depositing its evil eggs into my tree and I did not want to fend off a swarm of these bugs during the summer, so I sprayed it with Ortho. Next time I will read your blog first.

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  57. Today one of thoes flew out of NOWHERE ant tried to land on my friend face of course they F REACKED OUT but until now ive been calling it the nightmare wasp

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  58. Found one today in Columbus, Ohio. Nasty wind storm yesterday. One of its wings is damaged. It is beautiful to behold!

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  59. I saw some of these in my yard but also in the same log seen a larger version but all black almost twice or larger in its size with the long wiping tail. Still have no idea what the black one is they look similar in many ways in exception of color and size, would you know what is could be?

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    1. Leona, the one you describe that is all-black is likely the species Megarhyssa atrata. It should have had at least a little yellow, though, on the head and front legs.

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  60. We have at least 15 in our maple tree. Have never seen anything like them before.

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    1. They do get one's attention, don't they?!

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  61. I was letting our dog out when I saw this wasp on our porch. It REALLY scared me. Very glad to know it doesn't sting!

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  62. My wasps did not return this year. But since my last post they were returning yearly. Also worth noting the comment section went almost dead quiet for about 1 year. My video is still up, and a search for whip tailed wasps will return my two video as top results, thanks to bugerics blog and Mother Nature.

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  63. I saw one of these today and it was startling! It poked along a wooden table with what I thought was a stinger. Thanks for the info!

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  64. I was filming my son climb and walk across a big dead tree along the Arkansas river in Little Rock, AR and he suddenly stopped and said he was not going any further because of a crazy looking bug. I got this joker on video doing it's thing. We had no idea what it was, and found this article.

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    1. How cool! Thank you so much for sharing your story. :-)

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  65. Well I'm in Michigan and had one fly/fall next to me... I was immediately terrified... So because I didn't know if it were dangerous I captured it because i have small children... I also may have injured it's weird egg layer thing...if I let it go will it live? Also what do the adults eat?

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    1. Excellent questions. Yes, it should live, but they are common anyway. I'm not sure whether the adult wasps feed on *anything*. There are many insects that derive their energy as adults from burning the fat they accumulated as larvae.

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  66. I live near Pine Island 30 miles east of sault ste. marie Ontario and I seen a few of these wasps around a cut off dead tree stump. I have never seen one before and it was very interesting. It took me a while to find out the name of it. After some time, 2 of them disappeared and the 3rd flew into a nearby lilac tree.

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  67. I just had a female flying at our sliding door window for a good 15 minutes. Had no idea what it was. Crazy looking thing.

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