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Can anyone help with this fly? SW England, 09/07/2025. My first thought was Protocalliphora but the basicosta seems to be very pale.

James

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I'd also vote for Protocalliphora (and azurea is not the only species). The position of the wings and the preferred bird dropping support this.
Btw. I have problems to locate the basicosta here - even if lightening up.

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Hi Eric,

I quite agree with your remarks about the wings and the bird droppings!

There is only one Protocalliphora in the UK so I don't think that is an issue here. I would just like to be sure it is not a Phormia, which I have never seen. My ID key for British Blowflies cites 2 differences for Protocalliphora vs Phormia. One is the colour of the basicosta ( light in Phormia and black in Protocalliphora) and the other is the length of the acrostichals ( = half the length of the scutellum in Phormia and = the length of the scutellum in Protocalliphora). The lower calypter and the colour of the antennae are also different but I don't think we can use those features with my photos.

Here is another photo with the basicosta arrowed in red ( I think!)

James

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Hi James, I think your arrow points to the costagium, and the basicosta (on the right) seems to be very dark. I've excluded Phormia because we should see the pale anterior spiracle on your photos. The pre acrs are IMHO stronger than "twice the length of the hairs on top of the thorax". Olga Sivell (2021): Blow flies

Especially for the Chrysominae I often use: S. A. Marshall, T. Whitworth, and L. Roscoe (2011)
Blow flies (Diptera: Calliphoridae) of eastern Canada with a key
to Calliphoridae subfamilies and genera of eastern North
America, and a key to the eastern Canadian species of
Calliphorinae, Luciliinae and Chrysomyiinae
which is available at doi: 10.3752/cjai.2011.11

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I've been looking at the wrong bit again...Many thanks for your contribution: I will record this as Protocalliphora azurea.

James