Megaselia rufipes (Diptera: Phoridae): a new cause of facultative parasitoidism in Apis mellifera

Here we present the first report of the Phorid fly Megaselia rufipes as a “facultative parasitoid” of the honey bee Apis mellifera after its identification in a natural colony in the Piedmont Region of Italy. 60 bees with deformed wings probably caused by deformed wing virus and 50 healthy bees were collected. Whilst maintained in the laboratory, parasitoid larvae emerged from the deformed-winged dead bees; further examination revealed that the parasitized bees contained emptied body cavities. Parasitization was not detected in the normal honey bees. This finding suggests that M. rufipes should be considered among the facultative parasitoids of A. mellifera. As the parasite was found only in non-flying bees already destined for death, the M. rufipes damage seems unlikely to be important. However, this finding, and the role of Phorids in beekeeping generally, beg more study given the recent link of the Phorid Apocephalus borealis to its potential of one of the indirect causes of widespread honey bee losses in the USA.