Giant Ichneumon

What’s this bug??
Hello! Can you please identify this tree bug for me? Last summer at our cottage in the Eastern Townships (Brome Lake), Canada…I found several of these bugs burrowing into one of my trees. The tree is hollowed in several places by woodpeckers. These particular flying bugs that have about 4 inch long triple tail end tenticles that burrow into the tree, (all 4 inches of their tail end tenticles into the tree, and I must say only in this particular tree). They may be about 2 inches in length, and I also see some smaller brownish types around, but they do not react in the same way. The larger ones that appear to be darker in color, have a tail end that engulfs, and fans out into a whitish colored fan, that may grow to about the size of a nickle. Once their tail end fan appears at its’ largest, they retract it and fly away. I have never seen this bug before, and have owned my cottage for the past 25 years. Can you help identify, and explain what this bug is? I hope my pictures will be good.
Diane O’Donnell

Hi Diane,
The Giant Ichneumon, Megarhyssa atrata, is a beneficial insect that lays eggs in wood infested by boring grubs.

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