Megarhyssa wasps

Howard Russell, MSU Diagnostic Services - August 08, 2008

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Two people sent me photos of Megarhyssa wasps this week. One came from Jon Stauffer in Clinton County and the other from Cathy Patterson in Tuscola County.

The long-tailed Megarhyssa wasps (Hymenoptera: Ichneumonidae) are the largest ichneumons in Michigan. These impressive wasps frequently attract people’s attention because of their size and long tail-like ovipositor that is as long as or even longer than the body. The ovipositor has two sheaths which may make the insect look like it has three long tails. Do not panic; they will not harm you. The ovipositor (the bit that looks like a stinger) is for laying eggs not stinging people. The long flexible ovipositor is used to drill deep into dead or dying trees to deposit an egg into the body of a wood wasp or horntail larva. When the egg hatches, the Megarhyssa larva eats the horntail larva from within.

Megarhyssa wasp at work drilling into a tree.
Photo credit: Jon Stauffer, Majestic Tree Care in DeWitt

Note the long tail-like ovipositor.
Photo credit: Cathy Patterson, MSUE

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