In the UK and Europe, two species of solitary bees to look out for at this time of the year are Colletes halophilus and Colletes hederae.
The bee Colletes halophilus is found around the southern parts of North Sea coastal regions and has a preference for foraging at Sea Aster Aster tripolium flowers which are found on coastal saltmarshes. It nests along the sand dune-saltmarsh interface and can sometimes be found in large aggregations.
Slightly later, around mid September to October, Colletes hederae can be found in southern England where it is a recent colonist from Europe. As its name suggests, this bee is a specialist at feeding on the flowers of Ivy Hedera helix.
BWARS is running a mapping project for Colletes hederae so please report any sightings at the link above.