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blow fly - Bellardia vulgaris - male

blow fly - Bellardia vulgaris - Male
Milton, Norfolk County, Massachusetts, USA
October 28, 2017
Much like Bellardia bayeri but calypters whitish rather than brown and with four rather than three presutural dorsocental setae. Larger image.

Images of this individual: tag all
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Moved from Bellardia due to bicolored lower calypter and parafacial lacking dark spot

I agree with Bellardia vulgaris male. The upper parafacialia lack a consistent spot, both calypters are pale, the abdomen is strongly dusted and the distance of the dm-cu to the bend of the m vein is greater than two times the distance from the bend of the m vein to the wing margin (Rognes 1991). The images with red markings belong in the frass section as they depict nothing useful for separating species of Bellardia :-)

3 dc
I see 3 postsutural dorsocentrals with the first two a little more widely spaced.

re: 3 dc
Here's a blowup appearing to show four presutural bristles in a row. Are these dc's? They appear to be the 2nd row out from the center (I'd call the first row acrostichals):

I've also added five more images of flies I labeled Bellardia bayeri previously, and highlighted the presutural bristles in this row. I see that there are 3,3,4,2, and 5, respectively. There always seems to be a wide gap between the hindmost and the next one forward. The fly with two bristles (one reduced to a basal pit) seems to have lost some; the flies with more than three seem to double them up at the front end. I conclude that counting presutural dorsocentral bristles is not always a reliable species character.