Tuesday, 26 August 2014

Some Large Flower (or Hover) Flies... 

This large flower (or hover) fly, Sericomyia lata, has quickly become one of my favorites. About 20 mm (3/4") long, it's not as common as some of its relatives in the same genus but is memorable for its large size and its unusual, that is not-striped, abdominal pattern. Most of the genus are mimics of bees and wasps. Photographed at Roaches Pond on August 16th.

One of the better wasp mimics in the flower (hover) flies is the relatively common Spilomyia sayi. They have a habit of swishing their wings, I believe that's the technical term, from side to side as they move about on flowers in imitation of the raising/lowering of the wings of the typically black and yellow wasps that they mimic. This is a mating pair photographed south of Dollar Lake on August 20th.

The eyes of species in the genus Spilomyia can be incredibly patterned. This is the relatively rare, at least in comparison to S. sayi, Spilomyia fusca, also photographed south of Dollar Lake on August 20th. The tip of the abdomen, not visible here, is banded with white stripes that make this fly an excellent mimic of a bald-faced hornet, Dolichovespula maculata (though the hornet does not have eyes like this!).

The pièce de résistance for me is this unusually coloured blue flower (hover) fly. I first "discovered" and photographed this fly at three different locations last year and identified it, using Bugguide, as Didea alneti, the only blue flower (hover) fly in the guide. However a recent discussion on the Birding New Brunswick site suggests that it is actually in the genus Megasyrphus (although I can find no record or evidence of a M. latus, the suggested species on that discussion). So, again in conjunction with Bugguide, I believe it's either a blue variant of M. laxus (M. latus may have been a simple typo) or quite possibly an entirely new species of Megasyrphus. I've found this fly this year in four different locations but this photo is from the McIntosh Run in Spryfield on August 19th.

 

Added Note: Andrew Young of the Canadian National Collection of Insects, Arachnids and Nematodes has confirmed that this is Megasyrphus laxus (and notes that the unusual blue colour may be diet related and that it fades to yellow after death). Another Added Note: Turns out I was wrong...the blue flower flies I photographed at three locations in 2013 were all Didea alneti so all four locations where I found Megasyrphus laxus this year were new. See Two Blue Flower (or Hover) Fly Species! for the complete story...

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