Differs from the green and blue bottle flies at this site by being a dull slaty-gray in appearance, also slightly smaller. The green ones disappear around the end of summer; a larger, shiny blue-black one is disappearing while this one is still common mid-autumn.

Any way to distinguish calliphorid gender from images?

Other diptera notes from late Oct, lower Stevens Creek:
Lauxiniids abundant, all Minettia now; no more Homoneura.
Sarcophagids: One small sp and one med-large are always here; there probably are more at times, not sure.
Dolichopodids common, now all the reddish species, no more of the green Dolichus sp.
No more Stilleto Flies, common a month ago.
Tachinids: A couple of un-id’d spp still around, also X. bicolor. I’m no longer seeing a small brownish one that stalks and chases yellowjackets -- so far I’ve not been able to get a shot of the two together to illustrate the behavior; now yellowjacket numbers are diminishing... maybe next year. I'm expecting, but haven’t seen yet, the large Paradejeania Tach Fly that has a short flight season in November.
Syrphids: several species over the course of year here; now seeing only Toxomerus occidentalis and a few Eristalinus interrupta, not surprising as there’s almost nothing blooming now (some Epilobium and Stinging Nettle).
Bombyliids: Hemipenthes sinuosa still present. Villa lateralis seems to have disappeared but there is another Villa (?) that looks like lateralis but is much smaller -- will submit pix of the mini-villa some time.
Muscidae: Not abundant here any time; apparently only one sp now.
Anthomyiidae: Root-maggot flies are more abundant now than in other seasons.
Pipunculidae: No Big-headed’s down here, but I do find them higher up.
One small Tipulid present; many more in spring.
Haven’t seen a Scathophagid for a while -- they seem to be irregular; also there could be some Lesser Dung Flies here but I haven’t been working on them -- too small, and I’m concentrating on an odd little jumping “sand-bug” which I will submit when I get better pix of them (not easy).