I am very fond of these tiny little black and white flies, which go by the rather unattractive name of Root-maggot flies. Their Latin family name sounds a bit more appealing: Anthomyiidae. There are some agricultural pests in the family, like the cabbage root fly and the onion fly, which give the others a bad name.
I found all of these flies close to water; by the lago San Martiño, near the Playa Morouzos at the mouth or the Ria Ortigueira. There were two main species that I came across in August at this location: Anthomyia procellaris and Eustalomyia hilaris. At least I think that’s what they were!
These little anthomyiid flies are very widely distributed across Asia and Europe and vary considerably: a taxonomist’s dream or nightmare, I’m not sure which! The first one I saw had quite large black spots and seemed to match the descriptions and photographs of Anthomyia procellaris, but I cannot be certain.
When I looked closely at the photograph of ‘Anthomyia species fly on a leaf’ (above) I noticed that there was a little bubble of liquid below the head. Had it been drinking or was it blowing bubbles?!
The next species I came across in the same location, Eustalomyia hilaris (below), has a very pronounced black stripe running down the middle of the thorax, as well as black spots. Reportedly, this species is a parasite and its larvae develop within the larvae of bees (1). But another expert (Richard A. Jones) reports that it is “a nationally rare fly [in the UK] that breeds in the stores of dead flies collected by solitary wasps that nest in tunnels made in dead timber”. (4) Even more amazing!
I had the impression it was looking at me in the following photograph!
I relied on these excellent sites for my identifications (1, 2, 3).