While Lucilia blow flies may not be identifiable to species based on the key using pictures of the top, counting bristles (setae) can eliminate half of the choices.

L. sericata has three postsutural acrostichal bristles, marked P1, P2, and P3 here. Other species in the genus with three are L. thatuna, L. cuprina, and L. silvarum.

L. elongata normally has two but sometimes has two on one side and three on the other.

The rest have two (except possibly L. magnicornis, a far northern species which is implied but not stated to have two in the key).

Compare L. cluvia, which is missing this fly's P1:


Experts please correct my anatomy (or anything else).

Thanks to Terry Whitworth for producing the key to Calliphoridae and his email help identifying my picture.