On a coffee break last Sunday, we sat outside watching the goats in their temporary pen. Large logs from the dead portion of the maple tree outside our kitchen door remained where they’d fallen—the goats like to climb on them, and one long branch looks like a sculpture of a praying mantis. So we had not yet cut them up and moved them to the splitting pile. Half of the maple had been dead for some time, with branches breaking off occasionally during storms. A couple of weeks ago we finally had our former neighbor from Waterman Lake, Mark Krawiec, of Krawiec Tree Service, remove that portion in the hope of extending the life of the tree and avoiding a crash through our kitchen roof.
A lot of movement on one of the dead logs caught our attention. Upon closer examination we saw several bugs with lacey wings, a long red body with yellow and black stripes, and a black 3-inch “tail” walking along the log. Each bug appeared to feel, with its front feet, tiny holes previously bored into the log. When it found the right spot, it would do a handstand, raise its body in the air, and angle its long “tail” down, drilling it into the log. Once in place, it formed a bubble or transparent sack with an egg, and this disappeared down the tail.
A search online revealed that these fascinating bugs are Megarhyssa macrurus, or giant ichneumon wasps (one description can be found here: https://en.wikipedia.org/wiki/Megarhyssa_macrurus). The tail-like appendage is an ovipositor, used to deposit eggs on a host: larvae of the horntail wasp, which bores holes in decaying wood to lay its eggs. The Megarhyssa macrurus larvae consume the host.
No doubt our every step outdoors destroys some habitat unseen by us, however we now know that the dead logs are filled with life and so we will leave them until next summer, when the Megarhyssa macrurus emerge.