Looks like a dragonfly, with wasp-like markings
Sun, May 24, 2009 at 6:31 PM
I saw this insect on the side of my house, it was roughly 2 inches long with a similar wingspread. I’m assuming it’s some kind of dragonfly, based on the mouth, wings, and body. I’ve never seen one with markings like this though, it reminds me of a wasp, with striking yellow-on-black. I also don’t recall seeing a dragonfly with antennae ever before. Any idea what this guy is?
Kyle, Hatfield MA
Hatfield, MA

Male Giant Ichenumon

Male Giant Ichenumon

Dear Kyle,
This is a male Giant Ichneumon in the genus Megarhyssa.  Giant Ichneumons are parasitoids that are closely related to wasps, but they do not sting.  Your photo is of particular significance because of its high quality and also because we very infrequently receive images of male Giant Ichneumons.  In July 2007, we received a wonderful image of several males awaiting the emergence of a female.   BugGuide has a photo of a male Megarhyssa atrata, the species we believe you have photographed, and the posting contains a significant commentary posing the possibility that it might be a related species, Megarhyssa macrurus, also a possibility in your case.  Most of the images we receive of Giant Ichneumons are of females, and a large number are ovipositing.  The female has an ovipositor that can be as long as four inches, and many of our readers mistake this for a stinger.  The female uses her ovipositor to deposit eggs deep inside dead and dying wood that contains wood boring grubs, often the larvae of the Pigeon Horntail.

Update:  April 8, 2014
We are frequently asked if Giant Ichneumons can sting, and we always reply that they cannot.  We just found a fascinating article.  According to Icheumon Wasps by Lloyd Eighme on Skagit.wsu:  “It might frighten you, but if you could watch it long enough you would be amazed at what it does. It lands on the bark of a tree and crawls up and down, tapping with its long antennae, obviously searching for something. Eventually it finds the spot it is looking for and begins to drill into the bark with its long needle-like ovipositor. It has detected the larva of a horntail wasp chewing its tunnel in the wood an inch or more below the surface of the bark. The ovipositor is made up of three stiff threads, hardened by minerals, that fit together with a groove in the center. Vibrating those sharppointed threads forces them into the bark and sapwood of the tree to contact the horntail grub in its tunnel. An egg is forced down the ovipositor to parasitize the grub. If the ichneumon parasite larva killed its host, they would both die, trapped in the solid wood which the parasite is unable to chew. It only feeds on the nonvital organs like the fat body until its host has nearly completed its life cycle and has chewed its way out near the surface of the bark. Then it kills and consumes its host grub and completes its own life cycle to emerge as another giant ichneumon wasp in the genus Megarhyssa (mega=large; rhyssa=tail) to start over again. You can see both Megarhyssa and its horntail wasp host in the MG collection.
People often ask if the ichneumon wasps will sting them with their needle-like ovipositors. The wasps are interested only in laying eggs in caterpillars or other insects, but if you handle a live one it may try to sting you in self-defense. Small ones could not likely penetrate your skin, but larger ones might be able to

Location: Hatfield, Massachusetts

3 Responses to Male Giant Ichneumon, possibly Megarhyssa atrata, or maybe Megarhyssa macrurus

  1. jpx2610 says:

    We just found one in our back yard in Providence, RI. We have a cord of wood stacked near the house. Is this a benficial bug or a destructive bug? We have many large raised beds filled with vegatables, herbs, and flowers. Besides two cats.

    any thoughts?

  2. shawnee94 says:

    hi, i found a bug that looks just like this flying around my front door in the middle of the day… the only difference is that the tail is brown, not black. is it still a male Giant Ichneumon? i live in indiana, so i don’t know if this can even be here or if it is everywhere. i’ll put up pictures if i can. thanks!

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