This study was carried out in western Scotland (Dunbartonshire) where the Bombidae, though numerous, are represented by few species. Bombus lucorum L., B. agrorum Fabricius, B. hortorum L. and B. pratorum L. are all common, the first being perhaps the most abundant. Only two other species, B. terrestris L. and B. jonellus Kirby, have been seen and these infrequently. The colonies whose pollen collection was investigated were all obtained within a radius of about a mile (National Grid reference: 26/323808). Nearly all were dug up towards the end of their season, but some that were taken early in the summer were kept in observation nests until they died out. Details of the nests are given in Table i.