Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Clickable Guide
Moths Butterflies Flies Caterpillars Flies Dragonflies Flies Mantids Cockroaches Bees and Wasps Walkingsticks Earwigs Ants Termites Hoppers and Kin Hoppers and Kin Beetles True Bugs Fleas Grasshoppers and Kin Ticks Spiders Scorpions Centipedes Millipedes

Upcoming Events

BugGuide is a National Moth Week Partner. How to add your National Moth Week 2021 photos. July 17-25.

Photos of insects and people from the Spring 2021 gathering in Louisiana, April 28-May 2

National Moth Week 2020 photos of insects and people.

Photos of insects and people from the 2019 BugGuide Gathering in Louisiana, July 25-27

Discussion, insects and people from the 2018 gathering in Virginia, July 27-29

Photos of insects and people from the 2015 gathering in Wisconsin, July 10-12

Photos of insects and people from the 2014 gathering in Virginia, June 4-7.

Photos of insects and people from the 2013 gathering in Arizona, July 25-28

Previous events

Megarhyssa sp. - Megarhyssa macrurus - female

Megarhyssa sp. - Megarhyssa macrurus - Female
Montreal (downtown), Quebec, Canada
August 30, 2004

Images of this individual: tag all
Megarhyssa sp. - Megarhyssa macrurus - female Megarhyssa sp. - Megarhyssa macrurus - female Megarhyssa sp. - Megarhyssa macrurus - female Megarhyssa sp. - Megarhyssa macrurus - female Megarhyssa sp. - Megarhyssa macrurus - female Megarhyssa sp. - Megarhyssa macrurus - female

Can these be found in New Eng
Can these be found in New England?

Click on the tab above that says 'Data'
You will see all the places from which images have been submitted.

Moved from Orange and Brown.

I am speechless, what a series of photos! Welcome to Bugguide.

Bugguide looks like a very cool place to hang out for someone like me. Not really knowledgeable about insects and spiders but very willing to learn.

I only saw these Megarhyssa on two the evening on an old maple. A week later the maple had been cut down by the city.

Thankyou for the warm welcome.

Robert Ganz

these wasps parasitize horntail (sircidae) larave that are found in wood that is dying or dead. That is why they are not found all over the place. They are very specific on their hosts. If you are interested in learning more, a great great resource is Insects: Their Natural History and Diversity, by Stephen A. Marshall. I recommend this book for anyone starting in insects, or seasoned vets. Has great great photos and easy to understand keys. Check it out on amazon.

Ichneumonoidea kill trees?
Hello, we have a silver maple which dominates our back yard and is much beloved by our family. There are ichneumomoidea depositing eggs in one particular large branch. Does this mean the tree is dying? Will these wasps harm the tree? Thank you so very much!

Some ideas on this...
I'm not a tree expert by any means, but I'm somewhat familiar with some of the natural history here...and I certainly don't think the wasps can be hurting the tree. They would only be ovipositing on the tree if they sensed that there are horntail larvae under the bark feeding on the tree. The horntails would be causing more damage, and the Megarhyssa would be helping limit the horntails numbers. In that sense, Megarhyssa are generally considered beneficial insects.

If the number of horntails is not too large, and your maple seems fairly healthy otherwise, I'd think there's nothing particularly ominous about your tree having some horntail larva present and the attendant Megaryssa activity.

But if the tree is old and senescent (i.e. approaching death on its own) then that will often attract attention from more horntails and other pests (as older trees begin to lose their ability to fend off herbivores and pathogens as effectively as younger ones). If that's the case, what you're seeing may be a symptom indicating your tree is entering its last years. But the horntails (and certainly the Megaryssa) would be less of a cause, and more of an effect (of senescence).

Hope that makes sense...and that your beloved maple fares well :-)

Thanks for the info!
My kids are very happy that these crazy-looking insects are not hurting our "favorite tree". Thank you very much for your insights!

The tree may be dying, but not because of these gals.
They are laying their eggs on the things that are living in the tree, often Tremex larvae

The Megarhyssa larvae will consume the Tremex larvae, not the tree. Click on Megarhyssa and then on Info to learn more.

You can include a link to a book
if it has been entered on BugGuide. First, click on Search. Then select book and type Marshall, and search will return a link to the book. Click on the link and you will see that the book is assigned number 55904. Simply put Cite:55904 inside of square brackets and you will get a link to the book page like this (1). Nice eh!

Wow is right! I just saw, either this very same species or one very like it, ovipositing this afternoon. I live in Madison, Wisconsin, and this was in the University of Wisconsin Arboretum. I'm better at plants and birds than insects, but I was fascinated. Saw exactly what you captured in your photos: after she curled up her abdomen and inserted her ovipositor into the tree bark, a sort of translucent bubble developed at the tip of her abdomen. Is that an egg sac of some kind? Anyway, thanks for confirming what I saw.

For an explanation of the translucent disk...
...see the comment at the bottom of the previous image in this series. If you want even more info...check out this detailed article. (You can only see a one page preview from the given link. But at many public libraries, especially at universities, you could access the whole article.)

What a marvelous creation of nature...and a masterful series of photographs!!

Comment viewing options
Select your preferred way to display the comments and click 'Save settings' to activate your changes.