The above collage (full-size here) shows the dorsal abdominal view of my specimen (at center), together with figures illustrating the dorsal abdominal patterns of the best candidate taxa for this post gleaned from the keys in Vockeroth(1), Fluke 1933, and Fluke(1952). Note the top row shows females, the others are all males...and there can be (typically subtle) differences in the shape of the tergal markings and hairs between the sexes. The figures come from the following sources: Figs. 1 & 2 are from Fluke 1930; Figs. 12, 8, & 16 in the last column come from Fluke 1933; the others...Figs. 201, 130 & 127...are from Vockeroth(1).

While Vokeroth's key separates male Eupeodes americanus, E. fumipennis, and E. pomus based solely on characters of genitalia...the older key in Fluke(1952) indicated fumipennis has: "Pile of face black, wings brownish tinged". However the face in my specimen has mostly light (white) pile, except a relatively small area directly next to the antennae. Moreover, Figs. 130 & 16 for fumipennis show the yellow bands on tergites III and IV as wider and more emarginate & undulate than in my specimen. Figs. 130 & 16 are roughly consistent with the photo of E. fumipennis here.

Note that the epithet fumipennis means "smoky wings". and the wings in my specimen are brownish-tinged. However, again this photo of E. fumipennis has wings hyaline! Regarding wing infuscation, note that Osten Sacken(1877) remarked on one of his specimens that:

"Syrphus fumipennis Thomson, Eugenies Besa, 499 (California), seems to be very near my S. americanus and opinator, but does not quite agree with either. The slightly brownish tinge of the wings is not a character to be relied upon."
Each of E. americanus (=M. wiedemanni in Fluke), E. fumipennis, and E. pomus are described as differing from the individual in my photos in the following diagostic characters used in treatments of Vockeroth(1992) and Fluke(1952):

    1) all have the yellow spots of tergite II not reaching the outer margin;
    2) all have black or brown on their cheeks;
    3) all have a dark medial stripe along the forward edge of the face (i.e. below the antennae).

On the other hand, diagnostic characters given for S. opinator include the negation of the above three characters, which agrees with the individual here.

Indeed, Osten Saken's early 1877 key included a terminal couplet of the form:

Face with a brown stripe in the middle on the tubercle; abdominal cross-bands broad....americanus Weid. ♂Face and cheecks altogether yellow; abdominal cross-bands rather narrow....opinator n. sp., ♂ ♀
Over time, Johnson, Curran, Fluke, and others circumscribed more species from within what might be called the "americanus/opinator group", so the two clear and simple characters given by Osten Sacken above require amendments and refinements. The most important of these later species for this post is Metasyrphus lebanoensis Fluke...which has been put in synonymy with E. americanus but does not conform to characters 1) and 3) above. That species is what the post here keys to in both Fluke(1952) and Fluke 1933. The description of M. lebanoensis can be read here.

In light the above, it appears fumipennis and pomus can be reasonably eliminated from consideration here. For E. americanus, the situation is more complicated, since, as currently circumscribed, it is now a quite variable species due to the absorption of many forms via multiple synonymies. In particular, it includes the former M. lebanoensis, which is separated from the individual in my post only by having cheeks black...at least among the diagnostic characters used in the treatments of Vockeroth and Fluke. Whether this character alone is consistent and significant enough to reasonably eliminate E. (lebanoensis=) americanus from the running and give a confident ID of S. opinator is a question I can't answer with any authority. But based on the above analysis, it can be said that the somewhat tenuous assignment of S. opinator is the best we can do here...lacking a clear view to discern the "presence of hairs on the dorsum of the lower calypter" character, which would cinch a diagnosis of Syrphus.