A phorid fly known to be a parasite of bumblebees and paper wasps has been found to also parasitize honey bees. This fly, recently identified in California and South Dakota, is in the same genus as the “decapitating flies” that parasitize fire ants. The phorid flies, widely found across the US, multiply inside the bee hive and can infect the queen; female phorids deposit eggs into the abdomen of honey bees. Honey bees that are attacked by the phorid fly leave the hive at night and die. Then, the phorid fly larvae emerge from the dead bee and pupate elsewhere. The abandonment of the hive by worker bees is demonstrated in Colony Collapse Disorder, now thought to be caused by the interactions of multiple pathogens and parasites. Both phorid adults and larvae are found to carry honey bee deformed wing virus and Nosema ceranae, two pathogens associated with CCD. The researchers that detected the phorid flies parasitizing honey bees also found the infected bees flying from the hive at night, not a normal honey bee behavior. Honey bees infected with phorid flies were also found flying around lights at night in a manner similar to moths, also not a normal honey bee behavior. A potential threat exists if the phorid fly has moved from bumblebees’ small, seasonal colonies to infect the much larger, year-around colonies of honey bees. The entire report by Core et al. may be viewed at http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0029639.
One of the great mysteries of CCD is that not all colonies affected by the multiple suspected stressors--viruses, Nosema ceranae, and pesticides--collapse. Some of the beekeepers who have taken losses from CCD have questioned whether there is a triggering mechanism that brings about the collapse of colonies. The finding of phorid flies parasitizing honey bees may be an important clue to solving the CCD mystery. Today’s photo shows a paper wasp attacking a honey bee hive. A guard bee quickly responds to challenge and repel the intruder.--Richard