Cuckoo Bee

These wasp-alike bees are tiny, only 11-12 mm. They do not make their own nest but parasite the nests from the bees shown in my previous spotting (Andrena species). In fact I saw one getting into one empty nest from the Andrena fulva bees. I attach a video were it starts going around the nest. Finally, it went in and buried itself inside. Tough for the other bees! These compete with them for their nests.
I think the ones I have seen are females, based on the attached web site, since they show the red band in the upper part of the abdomen, right before the waist.