At the end of the afternoon this female Ectemnius cephalotus [1,2,3] hung around the bee hotels. Ectemnius females use bee hotels rarely as sleeping place [4,5]. She inspected several nest holes but eventually left. Possibly she is attracted by the smell of potential partners as they do use the hotels on daily basis as a sleeping place for the night and usually arrive at this time of day as well.
Literature
1 Nederlands Soortenregister2 KLEIN, Wim. De graafwespen van de Benelux. Jeugdbondsuitgeverij, Utrecht, 1996, 1-130. + KLEIN, Wim. De graafwespen van de Benelux: supplement. Jeugdbondsuitgeverij, 1999.
3 JACOBS, H. J (2007): Die Grabwespen Deutschlands Ampulicidae. Sphecidae, Crabronidae–Bestimmungsschlüssel in Blank, SM & Taeger, A (Hrsg): Die Tierwelt Deutschlands und der angrenzenden Meeresteile nach ihren Merkmalen und nach ihrer Lebensweise, Hymenoptera III–Keltern, Goecke & Evers, 79: 1-207.
4 Breugel, P. van 2014. Gasten van bijenhotels. – EIS Kenniscentrum Insecten en andere ongewervelden & Naturalis Biodiversity Center, Leiden.
5 Jacobi, Bernhard. (2001). Beutefang und Paarungsverhalten bei Ectemnius (Clytochrysus) cavifrons (Thomson, 1870) (Hymenoptera, Sphecidae, Crabroninae). 81 - 88.