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).
I am a retired entomologist with a background in quarantine pests and invasive invertebrates. I studied zoology at Imperial College (University of London) and did a PhD on the population dynamics of a cereal aphid (Metopolophium dirhodum) in the UK. I spent 5 years with the British Antarctic Survey studing cold hardiness of Antarctic invertebates and 17 years with the Food and Environment Research Agency. My main interests now are natural history, photography, painting and bird watching.