Studies of insect associates of bumblebees are not new. For example, Tuck (1896, 1897) reported over 50 species of insects associated with nests of British bumblebees. Sladen (1912) discussed nest associates and parasites of European bumblebees, and Plath (1934) published similar data for American bumblebees. Postner (1952) published more detailed data. He listed over 60 taxa of insects associated with bumblebees near Erlangen, Germany.
Husband, Richard W. and Brown, Thomas M.
"Insects Associated with Michigan Bumblebees (Bombus Spp.),"
The Great Lakes Entomologist, vol 9
Available at: https://scholar.valpo.edu/tgle/vol9/iss1/3