2017 March 4

 

   Where do flies go in winter?  Well, these two elected to spend the winter in a rotten log on southern Vancouver Island, where they were photographed by Leah Ramsay.  Although it is difficult to be certain of the exact identity, it is pretty sure that these are a species of cluster fly Pollenia sp.  Rob Cannings writes:  P. rudis used to be considered the sole species in North America, but recent revisionary work has resulted in six species, all found in British Columbia.  Five of these occur on Vancouver Island.  They are earthworm parasitoids and, as you might expect from their hosts, are introduced from Europe.  They are among the most common flies around in fall through spring as they overwinter as adults.  Sometimes they fly in warm winter days here; usually you see them sunning on warm walls.  They are duller looking than most blow flies (lack metallic sheen) and have characteristic crinkly yellow hairs on the thorax (sometimes not easy to see).

 

 Probably Pollenia  sp. (Dip.: Calliphoridae)  Leah Ramsay