The ‘Stump Stabber’ – An Ichneumon Wasp

"Echthrus sp. Family Ichneumonidae"

Echthrus sp., Family Ichneumonidae

Tap, tapping with antennae

While our daughter volunteered at Fort Edmonton this last weekend, my wife and I roamed the river valley around the fort. While we paused at a bench, I noticed a slender wasp ‘feeling’ its way across a fallen log. Its antenna were vibrating – a movement accentuated by the white bands on the antennae. I slowly went to my knees, doing the bug whisper thing (…don’ fly away, don’t fly away, pleeeease don’t fly away!)  I adjusted my equipment and began shooting as she explored the wood surface. Within moments she was raising her abdomen and her ovipositor began ‘drilling’  into the wood. The log was very close to the fixed park bench, and I struggled to keep her in the same plane as the camera – in this case it would have been an impossible task without my

Drilling begins

right-angle viewfinder. Her ovipositor slowly descended into the wood, leaving the protective sheath looped up behind the wasp. She was now intent on the task, so I moved in as close as my lens would allow, capturing the detail of the ovipositor as it entered the wood. She spent what seemed like a few minutes in that position, her ovipositor completely hidden in the wood. Then she began to move, drawing her abdomen upwards and slowly removing the ovipositor. She turned, gave the ovipositor a quick cleaning with her hind legs and then went on the search again, her antennae tapping along the log like a blind man with a cane. At this point I decided to try to see if I could obtain video of her behaviour, but the movements to remove my point and shoot camera from its case seemed to startle her and she flew off. I waited to see if she would return, but to no avail. (There, on my knees, I realised how valuable the new video-ready crop of DSLR’s could be…)

The ‘sheath’ loops back…

What was she doing laying eggs in the log? Ichneumon wasps are parasitic, so I knew she was depositing her egg directly on or in a larva of some sort within the log. I emailed a picture to the ever-helpful AlbertaBugs group, and it was not long before I received a reply. Marla Schwarzfeld at the U of A identified it to the genus Echthrus in the subfamily Cryptinae. She noted that the “…funky inflated front tibia” (see photograph in previous article) are features found on the females of this genus.

Marla’s I.D was a starting point for further research. (Without academic access privileges :-(, I could not find complete research documents, but often the abstract or first page information provided an outline of what was happening.) The vibrating antennae were actually tapping the wood, a form of vibrational sounding or echo location¹. This is where the enlarged tibia come in, as these have been shown to

Ovipositor at maximum depth

capable of sensing the vibration of the returning echoes². The female ichneumon’s vibrating antennae are testing for the hollow passages in the wood where grubs are burrowing. Once she locates a grub, she pierces the wood with her ovipositor, and then places an egg on, in or near the grub. When the egg hatches, the larva will begin to feed on the grub, eventually killing it. The ichneumon larva  will then pupate and eventually emerge from the wooden passage.

Darwin, when considering the claims of a beneficient intelligent designer, used the ichneumon as one example of why he could not believe  this:

But I own that I cannot see, as plainly as others do, & as I shd wish to do, evidence of design & beneficence on all sides of us. There seems to me too much misery in the world. I cannot persuade myself that a beneficent & omnipotent God would have designedly created the Ichneumonidæ with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice.”

Cleaning the ‘sheath’

The Ichneumonidae…slim, elegant wasps whose parasitoid efficiency helped support the grand idea that shook a superstitious world.

For more photographs of ichneumon wasps, visit

N.B. 10 June, 2010 – email (as forwarded by Robin Leech) from Andrew Bennet (Ag. Canada) in Ottawa confirms it as genus Echthrus and adds: “… the genus parasitizes wood borers, especially Cerambycidae.” (the Longhorn Beetles)

¹Laurenne, Nina,  Nikos Karatolos  and Donald L. J. Quicke. Hammering homoplasy: multiple gains and losses of vibrational sounding in cryptine wasps (Insecta: Hymenoptera: Ichneumonidae). The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 82–102.

²Broad, Gavin R.  and Donald L. J. Quicke.  The Adaptive Significance of Host Location by Vibrational Sounding in Parasitoid Wasps. Proceedings: Biological Sciences, Vol. 267, No. 1460 Dec. 7, 2000, pp. 2403-2409

³Darwin, Charles. A letter to Asa Gray, 22 May 1860

Enhanced by Zemanta
This entry was posted in Alberta, Canada, Hymenoptera, Ichneumonidae, macro, Parasitism, Summer and tagged , , , , , , , , .


  1. Ted C. MacRae 8 June, 2010 at 8:28 PM #

    Fascinating about the sound-reception capabilities of the legs – I’ve been waiting to see what that leg was all about.

  2. biobabbler 8 June, 2010 at 10:38 PM #

    awesome! and very cool ‘deep thoughts’ from the man. =)

    • Adrian Thysse 8 June, 2010 at 10:52 PM #

      Observing the process was certainly the highlight of the day!

  3. Dave 11 June, 2010 at 6:00 AM #

    Very nice post Adrian. One of the few interesting insects in the HBG the last gloomy week was a large black ichneumon with a white band across the middle of its antennae – but no ovipositor. I wonder if it was a wandering male Echthrus?

    ‘echthr’ – is a Greek root for hated or hatred, so I wondered if the author of the genus was channeling Darwin, but Gravenhorst proposed the genus name in 1829 according to Fauna Europaea, so I guess not.

    • Adrian Thysse 11 June, 2010 at 6:33 AM #

      The Moose Pasture may be a great location for these ichneumons, as they seem to prefer moist habitats. When I was Googling for more information on ichneumons I came across and article (The Amazing Ichneumon) that describes this situation:

      “I once found a broken ovipositor projecting from a log. Using a chisel, I followed the ovipositor 2 1/4 inches straight into the log. The ovipositor did not seem to follow a crack in the wood, but looked like it had been inserted directly into the tree. The ovipositor ended in a tunnel that appeared to be a larval tunnel of a horntail fly. I found dried insect parts inside the tunnel.”

      Sounds painful, but the ichneumon you came across may have been a female that had lost its ovipositor.

      BTW, do you know the technical name for the ‘sheath’ that covers the ovipositor? I couldn’t find that anywhere.

  4. Ted C. MacRae 11 June, 2010 at 12:46 PM #

    BTW, do you know the technical name for the ‘sheath’ that covers the ovipositor? I couldn’t find that anywhere.

    Valvulae (comrised of a left lateral valvula and a right lateral valvula).

    • Adrian Thysse 11 June, 2010 at 1:05 PM #

      Thanks Ted! I am now one valvulae (or two valvula) brighter!

  5. joan knapp 5 July, 2010 at 3:19 PM #

    Great photos and a fascinating account. Thanks for sharing

  6. Roast Garlicious 30 July, 2010 at 8:14 AM #

    excellent post, great photos!!!

  7. Julie Alexander 30 August, 2017 at 8:25 PM #

    My family of 4 were fascinated by seeing 4 Stump Stabbers on a new stump of a dead tree. Their ovipositors were in various positions, as were their contorting abdomens. We had never heard of or seen them before. Looking in the “wasps” section of Bugs of Ontario, by John Acorn and Ian Sheldon, we recognized the picture immediately.
    I haven’t seen any information about the males yet.

    • Adrian 31 August, 2017 at 6:17 AM #

      It is fascinating, and I have yet to come across another opportunity to photograph this behaviour again.

Post a Reply to Adrian Thysse

Your email is never published nor shared.