Móczár (1961) has reported some observations on the Stilbum cyanurum species, which parasites the mud nests of the Sceliphron destillatorium (Illiger) sphecid wasp. The female wets a point of the dry mud of the nest with a drop coming from her mouth parts and then touches it with her ovipositor. The operation, repeated a few times, brings to the penetration of the muddy wall and to the deposition of an egg into the cocoon of the Sceliphron. The Chrysidid ovipositor is very strong and indented, so it can be used to work like a knife. After the ovideposition and the extraction of the ovipositor, the wet mud is used to close the hole, leaving a visible depression on the cell wall. Berland & Bernard (1938) have listed many hosts for Stilbum cyanurum: Sceliphron, Eumenes, Chalicodoma and Megachile, all producers of mud nests.
A nice illustration is visible here (June 26th 2014 - Fully, Canton of Valais in Switzerland)
![Shocked :shock:](./images/smilies/icon_eek.gif)
http://www.youtube.com/watch?v=TPW97tpngyE
Source :
http://www.insecte.org/forum/viewtopic.php?f=3&t=132481