Club Horned Wood Borer Wasp

Size 11mm, some smaller wasps around, too. A few of these wasps were exploring the beautiful handmade tabe in our appartment. Last week, I have noticed small piles of sawdust on the table. Today, there was some wasp action going on under the table, with the wasps performing interesting processions. They normally touched down a few times at or near a tiny hole (diameter about 1mm). Eventually, it would land and either look around or enter the hole straight away. I rarely saw one entered individual come back out. Some individuals were covered in sawdust. The animal looks uniformely black, only the front leg joint seeming a bit reddish. Also the narrow and long abdomen looks like it has grey bands. The eyes are clearly grooved, disrupting an otherwise longish oval shape. The antennae are short and club shaped. The wings look a smoky grey with clear venation. They are wider at the end. The legs are longish, all thorned. This species is obviously a predator of young spiderlings, like to use holes made by wood boring insects. It is a species that is figuring on a local wasp census list with a few occurrences. I believe it is quite common, probably also as a consequence of the insect hotelmania in Switzerland increasingly noticed by the public.