Wing venation of Eristalis. Shows, especially, "spurious vein" (s), marked with stippling. This is a characteristic of most Syrphidae. (See also Flower Flies of Kentucky.)
Other labeled veins and regions:
h = humeral vein (a branch of Sc extending into humeral angle of the wing--ref = Borror Field Guide Insects), C=costal region, Sc = subcostal vein
R1, R2+3, R4+5 = radial veins (2+3 and 4+5 fused)
M1+2 M3 = medial veins (1+2fused)
Cu1, Cu2 = cubital veins
A = anal vein
More details later, I hope.
(From Comstock, Insect Life, fig. 556.)