I found this charismatic-looking wasp crawling up the back of my leg this morning.  I had neither the sang-froid nor the flexibility to photograph it where I found it, but it was extremely cooperative nonetheless.

The body of the wasp is about 1½ inches long, and its ovipositor, the long black thing trailing behind it, is another 5 inches or so.  My bug-identifying friend Jenn Forman-Orth let me know that it’s a wasp in the genus Megarhyssa, and also alerted me to its amazing life history.  Megarhyssa wasps parasitize the larva of horntail wasps, which live in burrows several inches into living trees.  My wasp is able to find the horntail larva by smell* through the wood, and then drills its ovipositor into the wood to lay an egg on the horntail larva.  There’s an amazing account here.  Nature is just delightfully weird.

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*From Bugguide:  “Horntail adult females introduce wood-digesting fungi (e.g. Amylostereum) when ovipositing, which helps their grubs extract food value while feeding on the wood. Adult female Megarhyssa are able to detect the odor of these fungi, and once they land on the bark of an infected tree the Megarhyssa will walk along tapping the surface with their antennae (or “antennating”) to further pinpoint the location of horntail grubs within the wood.”