This week's bee is Nomada goodeniana, Gooden's nomad bee. It is a cuckoo bee, laying its eggs in other solitary bees' nests, just as a cuckoo takes advantage of meadow pipits etc. Below is a female. She has no pollen brush (scopa) as she doesn't need to collect pollen. Unlike cuckoo bumblebees, which often resemble their hosts, nomad bees look radically different. This bee is a cleptoparasite of Andrena nigroaenea, which was bee of the week last week, and of A. nitida and A. thoracica.
This female Nomada goodeniana is investigating an Andrena nigroaenea nest hole, trying to decide if it is safe to enter.
Here are a couple exiting, having just laid an egg in the host's nests. When the egg hatches the larva will eat the host egg or larva and then eat the pollen which the host female has provided. It will develop alongside the host bees and emerge with them next spring to repeat the cycle.
Nomad bees do forage for nectar but are probably less efficient pollinators as they don't have hairy bodies. You can see how the antennae fold back out of the way as she goes deep into the flower.
This one looks pretty relaxed as he warms up in the sun.
Nomada goodeniana bees spend time foraging or prowling around their hosts' nest holes.
Nomada goodeniana is one of 34 British Isles species of nomad listed in Steven Falk's Field Guide to the Bees of Great Britain and Ireland. The nomad bees are all cletoparasites, as are around 30% of all bee species. Most solitary bees and bumblebees have one or more cuckoos that take advantage of them.