Phorid fly (Apocephalus borealis). Apocephalus borealis, phorid flies, have previously been associated with bumble bee parasitism [72] and have recently been described as a parasite of honey bees in the San Francisco Bay Area [73] . Phoridae family members (e.g. Pseudacteon sp.) are well-characterized parasites of ants and other insects. These flies lay eggs inside the insect hosts, which are in turn consumed by the larvae during development. Although, A. borealis parasitism of honey bees is uncommon, we analyzed our time-course samples for the presence of phorid rRNA by PCR. Pooled monthly samples were weakly positive for Apocephalus borealis in December and January ( Figure S3 ) and two individual hive samples produced robust amplicons. We sequenced PCR amplicons from two individual (September 2009 Hive # 7 and October 2009 Hive # 10) and one pooled-monthly (December 2009) samples and determined that the phorid rRNA sequences from our time-course shared 99% similarity to honey bee-parasitizing phorids captured in San Francisco. This is the first report of phorid flies in honey bee samples outside of California and thus expands their known geographic range (SD, CA), although the range A. borealis as a bumble bee pathogen extends across North America [74] .