This insect caused quite a stir when found on a tree at the WOLF playground because of its prominent "stinger." Although it looks dangerous, it is actually harmless unless you happen to be a tree.
|Wasp stinger with venom drop - Wikipedia CC|
|Horntail and ovipositor - Barry Stewart|
Siridicae's "horntail" seen above is really decorative, of no known purpose except to scare us. The female's ovipositor is beneath and much more flimsy looking. It uses it for the original purpose, in her case injecting an egg into wood. Imagine the pressure required to push a pin or needle into wood and compare it to the lightweight wasp body.
|Urocerus albicornis - Eric Adams|
|Ovipositor with sheath on either side - Stanislaw Kinelski, Bugwood.org CC|
"The wood wasp’s ovipositor looks like two hollow needles, one inside the other, each of which is lined with backward-facing teeth to give purchase as the wasp ‘drills’ progressively into the bark of a tree. This takes surprisingly little force, making it attractive for carrying out minimally invasive procedures such as brain biopsies without having to exploit a natural orifice."The only significant damage they cause is if a board used in your house construction contains the larva. When the adult emerges from its pupa it will chew its way out through wood, plasterboard or even a plastic covering. Please forgive it and understand what a cool insect is visiting your house.
More at blogs by Bugeric and the Bug lady.