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Home » Guide » Arthropods (Arthropoda) » Insects (Insecta) » Ants, Bees, Wasps and Sawflies (Hymenoptera) » parasitic Apocrita » Braconids and Ichneumons (Ichneumonoidea) » Ichneumon Wasps (Ichneumonidae) » Rhyssinae » Giant Ichneumons (Megarhyssa) » Megarhyssa macrurus
Photo#29174
Giant ichneumon wasp - Megarhyssa macrurus - female
Copyright © 2005 JCedar

Giant ichneumon wasp - Megarhyssa macrurus - Female
Arvada, Colorado, USA
August 21, 2005
Size: Varies, up to 3 inches!
I recently found a group of these feasting on an exposed section of an old tree in my yard. Size looks to range from ~1 inch to ~3 inches. They are leaving a lot of small holes in the tree. Please help me identify, I'm worried about my tree!
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Contributed by JCedar on 22 August, 2005 - 4:44pm
Last updated 24 October, 2007 - 5:04pm

Moved
Moved from Orange and Brown.
… john and jane balaban, 23 October, 2006 - 5:30pm login or register to post comments

Moved
Moved from Giant Ichneumons.
… john and jane balaban, 17 October, 2006 - 6:26pm login or register to post comments

Giant ichneumon wasp.
These insects are NOT sucking your tree dry. These are females of parasitic wasps known as giant ichneumons, genus Megarhyssa. We have many images in the guide, though yours may represent a new species for our site. The female uses her long ovipositor ("tail") to reach the larva of another wasp, the pigeon horntail, Tremex columba. She lays an egg on the horntail grub and her own larva will consume the horntail. So, this wasp may actually be SAVING your tree from horntail damage:-) Thanks for sharing. The holes here are the emergence holes of previous generations of horntails, or from some kind of beetle.
… Eric R. Eaton, 22 August, 2005 - 4:55pm login or register to post comments

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