There are 4 species of Eristalinus, a genus easy to identify thanks to their spotted/banded eyes.
-E. aeneus
-E. megacephalus
-E. sepulchralis
-E. taeniops
There is this very useful identification guide, but to point out the main differences:
E. taeniops is the easiest to identify because it's the only one with banded eyes, while the rest have spotted eyes.
E. megacephalus has a much lighter abdomen, with either white bands or big orange blotches.
E. aeneus and E. sepulchralis are the most similar ones, but while E. aeneus has a uniformly metalic abdomen, in the sides of segments 2 and 3 E. sepulchralis has pollinose areas. The eyes are also different, in E. sepulchralis they have more hair, and in the male they don't touch as in most hoverflies.
Helophilus is a genus of big, yellow colored hoverlies, with two species present in Galicia.
-H. pendulus
-H. trivittatus
While H. pendulus has a black vertical line on the face, and the basal 2/3rd of the hind tibiae orange, H. trivittatus has a orange line on the face, and only about 1/3 of the hind tibia yellow. The abdomen can also be somewhat different, with H. trivittatus having a lighter shade of yellow.
Parhelophilus is a similar genus with only one species in Galicia, P. versicolor, but they are much smaller, less brightly colored, and have orange antennae rather than black.
Sources:
https://www.flickr.com/photos/63075200@N07/collections/72157629445217282/
https://www.flickr.com/photos/63075200@N07/collections/72157630263217876/
https://www.biodiversidadvirtual.org/taxofoto/taxofoto/2041
There are 6 species, all of which can be found in Galicia.
-V. bombylas
-V. elegans
-V inanis
-V. inflata
-V. pellucens
-V. zonaria
They are easily identifyable with this helpful guide
