In the recent “City Nature Challenge” (an iNaturalist event co-hosted by our museum, LACM), the question was indirectly asked of me “how do you separate the common greenbottle flies,  classified in the calliphorid genus Lucilia, from the muscid lookalikes in the genus Neomyia that can also be green.” Especially, how would you tell them apart from the photos in iNaturalist, which are often not of stellar quality. My answer is to look them in the face. In both genera, the distribution of tomentum (microscopic extensions of the fly’s cuticle; not ‘hairs’ or setae, which are socketed) is different. The tomentose parts of the frons reflect light as silver or white, so this is often easy to see in photos.

You can see in Lucilia, on the left, that the tomentosity extends much farther up the frons, especially medially (in the middle) than in Neomyia, on the right, which has a dark, tomentosity- free section of the head.

You can see that the attached photo from iNat is a Lucila.