This tree bumblebee, Bombus hypnorum, queen has been visiting the garden in the last couple of days, with her fresh, striking tawny/black/white pattern very apparent. The last time I saw this species this year was in July, when males patrolled in the garden and queen bees could be seen searching for nest (or hibernation sites). August, three years in a row, yielded no sightings. Yesterday's queen visited Erysimum "Bowles's Mauve". This perennial wallflower, which often appears in BugBlog shots, and I highly recommend in any wildlife garden, has a very long flowering season and attracts a range of solitary bees and bumblebees, hoverflies and butterflies.
This graph shows the number of days per month I've seen this bumblebee in the last three years. Workers are active during May and June, most of the July activity is males marking and patrolling their flight paths and queens. The rest of the sightings in the autumn and early spring are queens feeding or nest searching.