Sphaerularia bombi Duford Parasitizing Bombus Queens in Northwestern Ontario

The initial spring loss of porential bumblebee colonies is the result of parasitism of the overwintered Bombus queens by the nematode Sphaerularia bombi Duford. The infested queens commonly have one or two nematodes in the body cavity and may have as many as six (Medler 1957), which effect sterility. Palm (1948) pesenied the histopathology of the nematode based on material collected in the vicinity of Lund, Sweden, where the infestation of the nematode was so intense that healthy queens were difficult to collect.