Lots of press coverage is swirling around our recent paper in PloS ONE: “A New Threat to Honey Bees, the Parasitic Phorid Fly Apocephalus borealis”, available here . Note, I use the term “our” advisedly, as I am 7th of 10 authors, and thus cannot take much of the credit for this work! Unfortunately, some of the press coverage this publication is garnering is incorrect, but I’ll let my colleagues at UCSF handle that on their website. What I’d like to concentrate on is the phoridological context of this story, particularly on the genus Apocephalus.
Genus Apocephalus consists of about 300 described species, virtually all of which are found in the New World. I am pretty sure that species described from other regions do not belong in a group with the rest of Apocephalus. In the 1990s, I revised about half of the genus, describing over 200 new species, but there are still many more out there. Right now I have a grant from the National Science Foundation to revise the rest of them.
Current classification of this group places the species in 2 subgenera: Apocephalus and Mesophora. Species of subgenus Apocephalus are the original “ant decapitating flies” like the ones I videoed in Brazil a few posts ago. Subgenus Mesophora have very different hosts, however. Most of the known species are parasitoids of fireflies and soldier beetles, an extremely different group of hosts from the ants the others attack. In addition, I have described a few species that attack stingless bees in the tropics.
One species always stood out, however, and that was Apocephalus borealis. This crazy thing had been reared from bumble bees, yellowjacket wasps, and a black widow spider! It seems as though A. borealis has an extremely wide range of host acceptability. Perhaps this is what allows it to switch into new hosts, such as honey bees. We know that honey bees were not the original hosts, because they are an introduced species in North America. Probably bumble bees are their main hosts, but who knows? This species is only recorded from North America.
My colleague, Dr. Paul Smith, and I are currently studying the relationships among species of Apocephalus using molecular characters (DNA sequences), as well as morphology (body structure). Once we have a good phylogeny of Mesophora, we should know more about how the flies have shifted hosts through the group.
Of course, besides many new species to be discovered, many described species do not have any studies about their way of life. Particularly intriguing are some species from Costa Rica that seem to be closely related to A. borealis. Perhaps they are parasitoids of tropical bumble bees, but nobody has studied this yet.
One other thing to note: Apocephalus borealis is far from the only phorid that parasitizes honeybees. In South and Central America, many species of Melaloncha bee killing flies will attack honeybees, and we have even seen the tiny, 1 mm long Styletta crocea trying to attack these relatively giant hosts. Finally, Pseudohypocera kerteszi is an occasional past in honey bee nests, although they are much more prevalent in the nests of stingless bees. I will write more about these other bee parasitoids in future blog posts, but you can see photos of the flies on my website phorid.net.
In summary, it’s great that some phorids are getting press, and I’m sure we are going to learn a lot about this species because of its agricultural importance. Kudos to the (other) authors for their fascinating work. Don’t forget, however, that Apocephalus borealis is only one of about 4000 described species, and many more have amazing life histories still to be discovered.