INCIDENCE AND EFFECTS OF 4 PARASITES IN NATURAL-POPULATIONS OF BUMBLE BEES IN SWITZERLAND

Field caught bumble bee (Bombus Latreille and Psithyrus Lepeletier) workers, males and queens were examined for the presence of 4 parasites. High prevalence of parasitization by conopid flies (20.2%) and the trypanosome Crithidia bombi (35.7%), moderate to low prevalence by the microsporidian Nosema bombi (9.0%) and the mite Bombacarus buchneri (3.6%) were found. Infestations by the 4 parasites were independent of one another but significant differences were found for bumble bee species and sex. Workers parasitized by C bombi were significantly less likely to forage for pollen and had developed ovaries in significantly more cases than did uninfested workers. Spring queens of B terrestris and B lucorum had lower prevalence of infestation by C bombi than was found in workers the previous summer.