I found this dangerous looking critter in 2017 and sent it to Bugguide, tentatively identified it as a horntail wasp in the family Siricidae. Now three years later I got a response that it is Sirex sp. Close enough for me.
Horntails are in the order hymenoptera like bees, wasps ants and the sawflies we recently discussed. They are xylophageous, meaning that they are herbivores that eat wood. That spike at the rear end is the ovipositor, an impressive drill that bores into the tree and deposits an egg and a fungus. Wikipedia describes it for Sirex noctilio like this:
"...as stiff and straight as a needle, polished black, with slight notches in the pointed half. It is hinged, to permit of its being turned at right angles to the body. . . the female selects a tree that is not too healthy, and settles on the bole; then, turning down her boring instrument on its hinge, she drives it through the thick bark to the solid wood."
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| Dorsal view - note ovipositor |
When the egg is inserted into the wood it is accompanied by a fungus that will digest the wood. Like many xylophageous beetles like the ambrosia beetle, the horntail has mycangia, pits that nourish and carry the fungus to where it lays the egg. insuring a food supply for its young.
The larvae hatch and begin tunneling through the wood for up to two years. Toward the end of their larval phase they dig their way up close to the bark before pupating. Once they emerge they only have to dig their way to the surface to fly away and mate.
I don't have a species identification of our Sirex but it isn't Sirex noctilio. This is the European wood wasp, a serious invasive species which causes the death of many pines in the Northeastern US. It hadn't reached Missouri in 2013 when MDC Discover Nature warned about its possible approach.
