At the end of the day under a setting sun, around 19:20, I was observing a lone Passaloecus wasp on the bee hotel busy closing her nest. Then an seemingly miniature version of the same wasp appeared that was clearly looking for a place to sleep. It had to be a Crabronidae so in order to see it better I caught it. Under the camera it turned out to be a male Spilomena, a genus of tiny wasps. This male is ±3mm in length.
It was very hard to get useful pictures but in the end it was clear this was a male S. Troglodytes, a rare species but the most common of the genus Spilomena in the Netherlands .
Male Spilomena have nicely looking yellow face.
The tiny wasp remained hyper active and would only stop for very short intervals which made it difficult to photograph the proper details. So I tend to photograph these active wasps in the evening and/or during the night because often they will become more slow, assumedly due to sleep. A trick that often works is covering the dish with the wasp for some time using a thick cloth so it turns dark and making the wasp relax and still. This also failed so I decided to wake it with a morning photo session. So I left the dish covered and with a fresh cotton filled with sugar water. Indeed the next morning the wasp was sitting very still. But on closer inspection he was not responsive at all and seemed exhausted. I tried to revitalize him with sugar water but failed as he would not drink any more and shortly after he passed away.
References1 Nederlands Soortenregister
2 KLEIN, Wim. De graafwespen van de Benelux. Jeugdbondsuitgeverij, Utrecht, 1996, 1-130. + KLEIN, Wim. De graafwespen van de Benelux: supplement. Jeugdbondsuitgeverij, 1999.